INSTRUCTORS GUIDE. FEMA P-593 CD, Seismic Rehabilitation Training for One- and Two-Family Wood-Frame Dwellings

Transcription

1 INSTRUCTORS GUIDE FEMA P-593 CD, Seismic Rehabilitation Training for One- and Two-Family Wood-Frame Dwellings ****************************************************************************** This Instructors Guide contains useful information that should be read by the Instructor before presenting this course. The first part of this Guide contains an overview and summary of the course; relevant background information; places this course in geographical context and describes similar, relevant courses; provides recommendations on how to tailor the content to your audience; and lists the course handouts. The second part of this Guide provides the Answer Key to the Student Exercises. ****************************************************************************** PART 1 The goal of the FEMA P-593 CD, Seismic Rehabilitation Training for One- and Two-Family Wood-Frame Dwellings is to promote seismic rehabilitation of one- and two-family dwellings, in order to reduce earthquake damage losses and increase dwelling habitability following moderate to major earthquakes. This is done by introducing the trainee to the effect of earthquakes on wood-frame dwellings, identifying common seismic vulnerabilities, and identifying rehabilitation approaches and available guidelines. The Applied Technology Council developed this training with funding provided by the Federal Emergency Management Agency. Comments and questions regarding this training should be directed to the Applied Technology Council ( Overview The following is an overview of the training, which is divided into seven parts. The number of slides and approximate presentation time is noted. There are Student Exercises, intended to immediately reinforce the training, included at the end of each part. The answer key to these exercises is at the end of this document. Part 1 - Introduces the training course, defines applicable terminology, and shows pictorially why seismic rehabilitation of dwellings is important. (25 slides/30 minutes) Part 2 - Introduces the effect of earthquakes on dwellings, discusses past performance of dwellings in earthquakes, and introduces partial seismic rehabilitation focused on vulnerable portions of the dwelling. (19 slides/30 minutes) 1

2 Part 3 - This is the heart of this training, introducing seismic vulnerabilities A through K, discussing how to identify vulnerable conditions, likely earthquake behavior, seismic rehabilitation priorities, and approaches to rehabilitation. It is recommended that this portion be included as a minimum. (88 slides/120 minutes) Part 4 - Clarifies that seismic rehabilitation work falls under the purview of the building code and building department, and gives a brief overview of code requirements applicable for voluntary and mandatory seismic rehabilitation. This section may need to be revised or augmented to be consistent with locally applicable seismic rehabilitation provisions. If possible, the instructor should research the locally adopted building codes prior to the training session. (12 slides/20 minutes) Part 5 - Addresses application of prescriptive provisions for anchorage to foundation and cripple wall bracing contained in the International Existing Building Code (IEBC) Appendix Chapter A3. The IEBC is used because it is a national-level model code, which most jurisdictions are likely to accept whether or not the IEBC is formally adopted. The acceptability should be verified with the local building department. The scope of the IEBC provisions and a step-by-step approach to rehabilitation design are presented. This part of the presentation will be of most interest to contractors and designers that will use these IEBC provisions, and plan checkers that will review designs using these provisions. If the local jurisdiction has adopted a modified version of foundation anchorage and cripple wall bracing, the local version should be substituted for the IEBC provisions. (49 slides/60 minutes) Part 6 - Introduces condition survey of the building prior to start of seismic rehabilitation activities. (13 slides/20 minutes) Part 7 - Provides a brief overview of important concepts for load path, and construction of shear walls and connections. (21 slides/20 minutes) In order to tailor this training to the particular audience and not exceed the time available, it may be necessary to pick and choose among these 7 parts. A combination of Parts 1 and 2 might be used to introduce a non-technical audience to the concept of seismic rehabilitation of vulnerable portions of dwellings. Part 3 should be at the center of most presentations to construction industry audiences. The trainer should feel free to choose among other parts as appropriate to the audience and time available. The presentation times above total five hours. Depending on your audience and how you run the training (will you allow yourself to be interrupted with questions, or will you hold questions/ discussion to the end?) the complete training might be compressed to 4 hours, or could take all day. It is recommended that the less technical the audience, the more you should compress the training. Remember that you will need to budget time for lunch and breaks. 2

3 Background There is a significant amount of guideline material addressing seismic rehabilitation measures available, but it resides in various places and in various forms. Therefore, the focus of this training is to provide an overall context for identifying and prioritizing seismic vulnerabilities requiring rehabilitation, and pointing the trainee to available guideline information. It is critical that contractors proposing rehabilitation measures to homeowners understand 1) how to prioritize seismic rehabilitation measures, and 2) the effectiveness of these measures. Without this understanding, rehabilitation work will not improve seismic performance, or may even reduce performance. This training offers priorities for rehabilitation work and describes the forces and movements the rehabilitation measures are intended to resist. It also identifies when prescriptive (conventional construction) rehabilitation solutions are available (which a contractor or homeowner can install without the involvement of an engineer or architect), and when rehabilitation design by an engineer or architect is needed. Regional Variations in Dwelling Construction There are significant regional variations in dwelling construction across the U.S. This training addresses wood frame dwellings supported on cripple walls, foundation stem walls or basement walls, with a primary focus on west coast construction practice. Some modifications to this training may be needed to address common construction practice in other regions. Additional guidance may be required in locations where there are local concerns regarding adequacy and performance of retaining walls. This training does not address (above grade) masonry wall dwellings. Other Training Courses There are other FEMA training courses available that address seismic rehabilitation of dwellings. Most notably, FEMA G225 Seismic Retrofit Training for Building Contractors & Inspectors is a course that is complementary to this training. While the FEMA P-593 CD Seismic Rehabilitation Training for One-and Two-Family Wood-Frame Dwellings focuses on identification and prioritization of vulnerabilities and guidance for rehabilitation design, G225 focuses on the nuts and bolts of installing seismic rehabilitation work. G225 is highly recommended as a follow-up to this course for persons who will be installing or inspecting seismic rehabilitation work. Other training courses have been developed in local areas to address dwelling anchorage to foundations and cripple wall bracing. These can also be considered complementary to this training. Audience This training is intended for those involved in building department policy decisions regarding seismic rehabilitation, and others who will be discussing seismic rehabilitation measures with homeowners (contractors, engineers, architects, plan checkers, etc.). This training assumes a moderate level of familiarity with dwelling construction and terminology. The audience may at times include homeowners, insurance and real estate industry persons, and others; some 3

4 additional explanation of terminology and concepts may be necessary for these audiences. It is also understood that the audience may include one or many of the audience types named above. While the entire training is meant to be presented to all of these audiences, some of the seven presentation parts might be removed or reduced for a particular audience. The trainer should review all sections before the training is held, determine the composition of the audience, and tailor the training accordingly. Handout Materials The FEMA P-593 CD contains: 1. The presentation slides (P-593 Seismic Rehabilitation Training Part 1.ppt Part 7.ppt). 2. An annotated bibliography describing available resources, in pdf file format (P-593 Annotated Bibliography.pdf). 3. Part 3: A pdf file (P-593 Vulnerability Card.pdf) of the vulnerabilities information. This pdf prints out as two 11 by 17 sheets, that can be copied back to back to get a card format. In addition, FEMA, ATC, the International Code Council, and Structures & Codes Institute have developed a CodeMaster laminated card entitled Residential Seismic Rehabilitation that incorporates this information and provides step by step instructions for use. Contact ATC, Structures & Codes Institute, or ICC regarding copies of the CodeMaster. 4. Part 4: A pdf file (P-593 Code Citations.pdf) of building code citations is provided for those interested in the details of applicable building code sections. This file is based on the 2006 International Building Code, International Residential Code, and International Existing Buildings Code. 5. Part 5: A pdf file (P-593 Step-by-Step.pdf) is provided in 8½ by 11 format giving a step by step method for implementing the Appendix Chapter A3 provisions of the International Existing Buildings Code. The methodology parallels the Part 5 presentation, but provides a form that can easily be taken to a job site and implemented. (Note that the presentation handouts are described in the closing slides of Part 1 of the presentation. These slides should be adjusted to reflect the handouts that will be provided at your training.) 6. The trainer may want to create printed handouts from the.pdf of the presentation slides for future reference of the trainee. 4

5 Student Exercises: Part 1 - Introduction PART 2 STUDENT EXERCISE ANSWER KEY 1.1 Name at least two ways in which seismic rehabilitation of wood-framed dwellings can lead to improved home safety. Protecting occupant safety, reducing structural damage, making home more likely to be habitable following an earthquake 1.2 What might be the effect on your community if many dwellings can t continue being occupied following an earthquake? Answers may vary - goal of question is to prompt discussion of difficulties caused. Relocating residents in emergency shelters reduces their ability to resume normal daily activities and puts demands on emergency shelter operators. Often school facilities are used for emergency shelters, hindering the ability of schools to resume functioning. Student Exercises: Part 2 - Earthquake Behavior & Approaches to Rehabilitation Identify whether the following statements are true (T) or false (F): T / F 2.1 Wood-framed dwellings are generally a very safe place to be in an earthquake. The home is one of the safest places to be. T / F 2.2 Partial seismic rehabilitation is less cost effective than complete seismic rehabilitation. Partial seismic rehabilitation is more cost effective because it allows available funds to be spent correcting the most vulnerable portions of the building. T / F 2.3 Unreinforced masonry chimneys have been vulnerable to damage in past earthquakes. Unreinforced masonry chimneys have been damaged in virtually every moderate or larger earthquake on record. T / F 2.4 Dwellings without bolts to the foundation do not get damaged in earthquakes. Dwellings without bolts to the foundation have repeatedly been damaged in moderate and larger earthquakes. T / F 2.5 Dwellings with little or no bracing walls do not get damaged in earthquakes. Dwellings with little bracing have been damaged repeatedly. 5

6 T / F 2.6 Hillside dwellings have been vulnerable to damage in past earthquakes. Hillside dwellings suffered damage and collapses in the Northridge Earthquake. Student Exercises: Part 3 - Seismic Vulnerabilities and Seismic Rehabilitation Concepts 3.1 What is the priority of seismic rehabilitation for the following conditions: high (H), medium (M), low (L), or varies? H / M / L / varies H / M / L / varies H / M / L / varies H / M / L / varies H / M / L / varies a. Providing anchor bolts for a dwelling not currently bolted to its foundation. b. Installing plywood or OSB sheathing on unbraced cripple walls. c. Strengthening dwelling fronts with open-front conditions where there is little bracing wall and no seismic detailing d. Providing anchorage for unanchored veneer. e. Anchoring the top and bottom of 14 foot high posts 3.2 Name at least two vulnerabilities that have prescriptive measures for design of seismic rehabilitation (no engineer or architect required)? Dwelling to foundation anchorage, cripple wall bracing, bracing of open-front dwellings, inadequate shear wall length, anchorage of posts, anchorage of decks, stairs, roofs 3.3 Name at least one vulnerability that requires an engineer or architect for rehabilitation design? Split-level dwelling, hillside dwelling 3.4 List the potential seismic vulnerabilities that should be evaluated/looked for in this dwelling: Figure 3-1 Single-family dwelling with split level construction 6

7 Water heater (always check) Chimney Split level Open front Dwelling to foundation anchorage Cripple walls under single-story portion (cripple walls may or may not occur. It is wise to check when the first floor level is noticeably above exterior grade. 3.5 List the potential seismic vulnerabilities that should be evaluated/looked for in this dwelling: Figure 3-2 Single-family hillside dwelling Water heater (always check) Hillside dwelling Student Exercises: Part 4 - Building Code Requirements for Seismic Rehabilitation 4.1 What types of work require conformance to the locally adopted building code (circle all that apply): a) Voluntary seismic rehabilitation b) Mandatory seismic rehabilitation c) Additions and alterations d) Anchoring book shelves 7

8 4.2 What types of work require a building permit (circle all that apply): a) Voluntary seismic rehabilitation b) Mandatory seismic rehabilitation c) Additions and alterations d) Refinishing counter tops 4.3 Which of the following might be used for guidance for seismic rehabilitation measures (circle all that apply): a) International Building Code (IBC), or locally adopted building code b) International Residential Code (IRC), or locally adopted residential code c) International Existing Building Code (IEBC) d) Locally adopted rehabilitation provisions Student Exercises: Part 5 - Prescriptive Seismic Rehabilitation Plans Figure 5-1 Cripple wall and foundation plan of two-story single-family residence, with proposed cripple wall bracing locations shown 8

9 Answer questions 5.1 to 5.6 based on Figure 5-1 for a two-story wood-framed dwelling with stucco exterior and a composition shingle roof: 5.1 Do the proposed cripple wall bracing panels meet the required amount of bracing for the IEBC (heavy solid line shows the extent of cripple wall sheathing, dimension is the length of bracing)? Why or why not? Table A3-A, for two-stories and all other conditions requires that 50% of the cripple wall length be braced. Line A is adequate at 20 ft, Lines C and D are adequate at 10 ft. Line 1 is adequate at 12 ft, and Line 3 is adequate at 15 ft. 5.2 Do the proposed cripple wall bracing panels meet the required placement of panels for the IEBC? Why or why not? IEBC requires that the panels be placed at each end of the wall (to the extent possible) and distributed along the wall length. The plan meets these criteria. 5.3 The cripple wall is 30 inches high. Do the proposed cripple wall bracing panels meet the height-to-width ratio requirements of the IEBC? Why or why not? IEBC requires that the width of plywood not be less than two times the plywood height. This requires a plywood width of not less than 5 ft. One bracing panel is 4 ft, and does not conform to IEBC. 5.4 How many 1/2-inch diameter anchor bolts are required along Line 3 based on IEBC maximum bolt spacing requirements? IEBC Table A3-A for two-story dwellings requires 1/2-inch anchor bolts at not more than 4 ft on center. Line 3 would require not less than eight bolts. 28 /4 = 7 spaces = 8 bolts 5.5 If the sill plate along Line 3 is made of two ten-foot lengths and one eight-foot length, how many 1/2-inch anchor bolts are required? IEBC Table A3-B requires four anchor bolts each piece of sill, for 12 bolts total. 5.6 What type and size of washer is required on the anchor bolts? IEBC Figure A3-3 requires a steel plate washer to less than 2 x 2 x 3/16 inches. Student Exercises: Part 6 - Condition Survey 6.1 Which of the following might be identified during a pre-construction condition survey (circle all that apply): a) Excessive moisture in the crawlspace that might lead to wood decay b) Unusual framing conditions that might require alternate rehabilitation details 9

10 c) Termite damaged framing members d) Decay damaged framing members e) Hidden decay - there will always be some possibility of decay uncovered during construction, this must be planned for. 6.2 What is the benefit of identifying the conditions in Question 6.1 prior to start of construction? This allows additional scope, duration, and cost of work to be dealt with in a systematic fashion. Student Exercises: Part 7 - Basic Concepts of Seismic Rehabilitation Construction 7.1 Which of the following can reduce the effectiveness of a shear wall (circle all that apply): a) A nail that is smaller than the specified size b) A nail of the same pennyweight, but not designated as common c) Nails less than 3/8-inch from the plywood edge d) Nails installed to that they do not penetrate through plywood to framing behind (shiners) e) Overdriven nails 7.2 Which of the following are important to the effectiveness of an adhesive anchor to the foundation (circle all that apply): a) Cleaning out the drilled hole and removing all fines b) Providing enough adhesive so that the hole is completely filled when the bolt is installed c) Pre-loading the adhesive anchor with a torque wrench - this is not recommended, as any pre-tension will go away due to creep of the adhesive d) Providing steel plate washers 10