I was hoping i could get some input as to what items to pay atten. Pdf evaluation of overstrength factor of steel moment resisting. Where the design story drift is obtained from first order analysis, it should be increased by an incremental factor ad, or a p. Fema 451b topic 9 handouts seismic load analysis 2 instructional material complementing fema 451, design examplesseismic load analysis 9 7. Minimum design loads for building and other structures supplement no. Ghosh 2014 61 values that have a 2% probability of being exceeded in 50. Fema 451b topic 9 handouts seismic load analysis 2. The connections of such discontinuous elements walls or frames to the. March 31, 20 use in conjunction with asce 7 10 second printing or with asce 7 10 first printing and errata 1 and 2. The seismic load effects including overstrength factor in accordance with sections 2. Where the load combinations with overstrength factor in section 12.
Chapter 7 asce 710 design provisions for structures with passive energy dissipating systems 5. Correctly define the different spectral parameters used to define the seismic hazard in asce 7. On the contrary, in the us codes there are factors that quantify separately the redundancy and overstrength of a structure. Pdf using inappropriate system overstrength factors may lead to weak seismic performance or uneconomic results. Significant changes from asce 705 to asce 710, part 1. The basic combinations for strength design with overstrength factor in lieu of equations 165 and 167 in section 1605. In aci 31811 and ascesei 710 an overstrength factor. Ive been searching the web for a sort of comprehensive list of what elements get designed for the overstrength factor. Instructional material complementing fema 451, design examples seismic load analysis 9 7. Chapter 7 the asce 710 design provisions for structures with. Seismic design specification for buildings, structures. Asce 7 05,1 the standard referenced in the 20062 and 20093 editions of the ibc, did not undergo the recently usual threeyear update. These load combinations and their applicability are examined in section 2.
Scaling of base shear results of static and dynamic analysis. Accounting for ductility and overstrength in seismic. Structure magazine seismic design of nonstructural. Clarification of the requirements for anchor overstrength and. Moore, a structural and civil engineering firm with offices nationwide. Structure magazine the most common errors in seismic.
A guide for practicing engineers applied technology council. The mapped peak ground accelerations in asce 7 10 fig. It is required where it is explicitly stated in the code. Three seismicforceresisting coefficients are used to gauge the performance of these systems, helping designers and engineers select the right one for their application. Minimum design loads for building and other structures. Asce 705 requirements for seismic design categories c and above where ductility. Lateral force design was carried out according to ascesei 710. An integral part of building codes in the united states, minimum design loads and associated criteria for buildings and other structures asce sei 7 16 describes the means for determining dead, live, soil, flood, tsunami, snow, rain, atmospheric ice, earthquake, and wind loads, and their combinations for general structural design. Seismic system factors and system overstrength free download as powerpoint presentation.
The 2014 nehrp provisions will use asce 710 as the base document, making modifications. Effects the stability coefficient, shall not exceed, max, value given by asce 7 eq. What are the asce 710 seismic overstrength load combinations. Loads and load distributions shall not be less than those given by asce 7 nehrp. Asce 7 minimum design loads for buildings and other structures, american society of civil engineers, 1998. Recently, a study was conducted to investigate the overstrength factor of. Equivalent lateral force procedure elf response is defined by two modes. Ive not been able to find a good explanation of what these are used for. Minimum design loads for buildings and other structures.
He is a member of the building seismic safety councils 2014 provisions update committee and of the american society of civil engineers seismic subcommittee for asce 710. An evaluation of overstrength factor of seismic designed low. New concept used to approximate the combined effects of higher modes that may be significant to story velocity. The results show that mrf, cbf, and semirigid steel frame would be subjected to a base shear up to 4. Evaluation of overstrength factor of steel moment resisting frames. Code considerations related to woodframe shear walls and diaphragms are discussed, including failure modes of wood shear walls and the detailing required to provide ductile behavior.
It is incorporated in the third printing of ascesei 710 only. Pdf use of overstrength and inelastic response in seismic design. Seismic design of nonbuilding structures structure magazine. These studies have shown in their globality that the overstrength depends on different factors which the most important of them is member ductility factor. When reinforcement is used to restraint concrete breakout, the overall anchorage. When the new code came out 2006 ibc, some colleagues and i came to the conclusion that equations 58 of asce 12. The omega overstrength factors should only be used where specifically. Evaluation of overstrength factor of steel moment resisting.
Evaluation of the overstrength factor for nonstructural. Reinforced concrete frame members not designed as part of the seismic forceresisting system shall comply with section 21. These values are much less than the strength capacity of the steel frames with considerable response modification factors which are the combination of. He is a member of the asce task committee on anchor rod design, and an associate member of the joint aci. Differences in the ibc and ascesei 7 load combinations are covered in the following sections. Seismic design of castinplace concrete diaphragms, chords. It is recommended that the user make use of the ascesei 710 expanded seismic commentary, which provides 5 pages of valuable background information. Reflection amplification factor, cd, fot use in asce 710 sections 12.
Seismic design of wood structures in the context of. Because earthquake loads together with the wind loads considerations have a huge impa. Table 1 horizontal earthquake acceleration values for experimental. Design examples seismic load analysis 9 84 asce 705 ground motion selection. Risk categories of buildings and other structures are shown in ibc table 1604. Seismic design requirements, as stated in section 11. It is recommended that the user make use of the asce sei 7 10 expanded seismic commentary, which provides 5 pages of valuable background information. Asce 716 provisions for lateral drift determination civil. Seismic stability properties of wood building materials. Modern steel constructions monthly steel quiz tests your knowledge of steel design and. Use in conjunction with asce 710 second printing or with asce 710 first printing and. Asce 7 minimum design loads for buildings and other structures, asce 7, 1998. Seismic system factors and system overstrength strength of. Overstrength factor and allowable stress design asce 705.
Jul 03, 2019 pdelta effects must be considered, per section 12. The level at which the horizontal seismic ground motions are considered to be imparted to the. Values of f pga in the table are identical to the shortperiod site coefficient fa in asce 7 10 table 11. Asce 7 2006 recommends a factor of 23 to reduce the mce to obtain the design hazard level. The first mode effect is reduced by the rfactor of the seismic forceresisting system, but then amplified by the overstrength factor. Seismic loads based on ibc 2012asce 710 based on section 16. Seismic design specification for buildings, structures, equipment, and systems. Using the reliability procedures described in that publication, wellconfigured structural systems conforming to the requirements of asce 7 and its referenced standards can be shown to generally meet these. Frequently misunderstood seismic provisions of asce 710. Design of anchor reinforcement in concrete pedestals. Chapter 12 seismic design requirements for building structures. Mandatory retrofit program for wood frame buildings with.
A seismic analysis in the design of buildings especially high rise towers is a very important factor to consider. The equivalent lateral force procedure is a linear static analysis technique that approximates nonlinear building response by use of the response modification factor r, which accounts for a buildings inherent ductility and overstrength. Asce 7 groups woodframe seismicforceresisting systems table 12. Pdf using inappropriate system overstrength factors may lead to weak seismic. Design loads for seismic design based on asce 7 05. Design of anchor reinforcement in concrete pedestals widianto, chandu patel, and jerry owen widianto is a structural engineer on the shell suex 1 project. We are going to cover the basics and some commentary. Seismic forceresisting system asce 7 section where detailing requirements are speci. Design of anchor reinforcement in concrete pedestals widianto, chandu patel, and jerry owen. Application of overstrength factor how deep does it go. Design examples seismic load analysis 9 95 asce 702 response parameters for. Would someone please enlighten me as to the purpose of asce 7 10s seismic overstrength load combinations.
I understand how to apply it, just not particularly to which items. With the simplified procedure of asce 7, section 12. Sfrs components that require application of the overstrength factor are defined in asce 7 minimum design loads for buildings and other structures and others are only found in the seismic provisions. The most common errors in seismic design and how to properly avoid them thomas f. The overstrength factor increases the required seismic forces and is applied in specific cases or in the design of certain parts of the structure. Asce 7 16 established the acceptable collapse probabilities based on work reported in fema p695 quantification of seismic performance factors.
Seiasce 702 minimum design loads for buildings and. Asce 7 2006 associates the design hazard to the maximum considered earthquake mce which corresponds to 2% probability of exceedance in 50 years in most parts of the us, except in coastal california leyendecker et al. Chapter 12 seismic design requirements for building. Your understanding is correct, but for one exception in asce 7 10, 7 16 section 12.
Chapter 7 the asce 710 design provisions for structures. When using allowable stress design, factor of safety for soil bearing values shall not be less than the overstrength factor of the structures supported. Are they to be applied just to the connections or to both connections and member design. March 31, 20 use in conjunction with asce 710 second printing or with asce 710 first printing and errata 1 and 2. Response modification factor of reinforced concrete moment resisting frames in developing countries by adeel zafar thesis submitted in partial fulfillment of the requirements for the degree of master of science in civil engineering in the graduate college of the university of illinois at urbanachampaign, 2009 urbana, illinois adviser. Asce 7 says, where specifically required so you simply have to keep your eyes open for references to section 12. Asce 716 provisions for lateral drift determination. Seismic system factors and system overstrength strength. Expanded seismic commentary asce 7 seismic provisions. When to and when not to use the overstrength factor.
A guide for practicing engineers nist gcr 89171 jack p. Jan 05, 2018 frequently misunderstood seismic provisions of asce 7 10. Pacific earthquake engineering research center guidelines for performancebased seismic design of tall buildings may 2017. Seismic load effects including overstrength factor 6. American society of civil engineers seismic subcommittee for asce 710. Overstrength and ductility factors for steel frames. Structure magazine the most common errors in seismic design. Asce 7 permits the use of the equivalent lateral force procedure for the design of most buildings, except. Asce 7 10, aisc 36010, asic 34110, aci 31811 including chapter. I want to use allowable stress design in combination with the overstrength factor.
For those who own a first or second printing, you may download a pdf file of the commentary for free from the asce website. A comparative study of design base shear for rc buildings. Pdf evaluation of overstrength factor of steel moment. Determine the elements that must be designed using the load combinations including the overstrength factor. Importance factors, ie, are shown in asce 710 table 1. Shafts under lateral loads, users manual and technical manual. The basic combinations for strength design with overstrength factor in lieu of equations 165 and 16 7 in section 1605. Though implemented into these codes with the same mechanisms as the overstrength factor for building structures, the rationale behind its inclusion for anchorage was fundamentally different. Earth retaining structures tanks and vessels telecommunication towers stacks and chimneys.
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