new seismic design requirements in louisiananew seismic design ... established knowledge about the...

2011 Louisiana Transportation Conference

New Seismic Design Requirements in Louisiana

SDR Engineering Consultants, Inc.January 11, 2011

Mohsen Shahawy, PhD., PE


Seismic Zones. Until relatively recently, seismic design criteria depended solely upon the seismic zone in which a structurewas located. Zones were regions in whichseismic ground motion, corresponding to acertain probability of occurrence, was within certain ranges.


New design requirements recognized that structure performance during a seismic event depends not only on the severity of sub-surface rock motion, but also on the type of soil upon which a structure is founded


The soil condition at the site is the additional variable that must now be dealt with.

While this adds another element to an already complicated procedure, it does incorporateestablished knowledge about the effect of soil properties during an earthquake intoseismic design criteria.


In general, the process leading to the classification of the Seismic Design Category involves several steps and clearly, the procedure for establishing the seismic classification of a structure has become more complex.


Develop the Seismic Zone classification map for Louisiana based on a study of all parishes in the state and accounting for the existing soil classification for each Parish.

Objectives


ProcedureStep 1: Site Class Definitions

A site shall be classified as A though F in accordance with the site class definitions.

Table 1. Basis for Seismic Design Criteria in Model Codes and Standards

Seismic Zones Seismic Site Classification

Classifications 0, 1, 2, 3, 4 A, B, C, D, E, F

Criteria for Classification

LocationLocation, Structure Use, & Soil Type


ProcedureStep 2 : Determine Peak Ground Acceleration coefficient

(PGA) and the short- and long period spectral acceleration coefficients (SS and Sl , respectively)

Step 3 : Determine zero, short, and long-period sitefactors, FPGA , Fa , and Fv


Procedure

Table 1. Basis for Seismic Design Criteria in Model Codes and Standards

Step 4 : Calculate the Response spectrum


For each Parish:

Divide into 3 or 4 zones based on Zip code

Perform analysis and determine SD1=Fv*Sl

Determine Zone Classification


AccelerationCoefficient, S

D1Seismic Zone

S ≤ 0.15 1D1

0.15 < S ≤ 0.30 2D1

0.50 < S 4D1

0.30 < S ≤ 0.50 3D1

Seismic Performance ZonesEach bridge shall be assigned to one of the four seismic zones in accordance with Table 3.10.6-1

Table 3.10.6-1 Seismic Zones


Parish Zip code PGA Ss Sl

Site Class FPGA Fa Fv SD1=Fv*Sl As=FPGA*PGA Zone

Acadia70543 0.027 0.06 0.028 D 1.6 1.6 2.4 0.07 0.043

170578 0.027 0.059 0.028 D 1.6 1.6 2.4 0.07 0.04370526 0.026 0.059 0.028 D 1.6 1.6 2.4 0.07 0.042

Allen70648 0.028 0.062 0.029 D 1.6 1.6 2.4 0.07 0.045

170655 0.028 0.064 0.03 D 1.6 1.6 2.4 0.07 0.04571463 0.031 0.07 0.032 D 1.6 1.6 2.4 0.08 0.050

Ascension

70737 0.029 0.064 0.029 E*2 2.5 2.5 3.5 0.10 0.073

170778 0.029 0.063 0.029 E* 2.5 2.5 3.5 0.10 0.07370774 0.029 0.064 0.029 E* 2.5 2.5 3.5 0.10 0.07370769 0.029 0.065 0.03 E* 2.5 2.5 3.5 0.11 0.07370346 0.028 0.062 0.029 E* 2.5 2.5 3.5 0.10 0.070

Assumption70390 0.027 0.058 0.027 E* 2.5 2.5 3.5 0.09 0.068

171355 0.025 0.055 0.026 E* 2.5 2.5 3.5 0.09 0.063

Beauregard

70634 0.03 0.067 0.03 D 1.6 1.6 2.4 0.07 0.048

170653 0.03 0.066 0.03 D 1.6 1.6 2.4 0.07 0.04870652 0.029 0.063 0.029 D 1.6 1.6 2.4 0.07 0.04670660 0.028 0.063 0.029 D 1.6 1.6 2.4 0.07 0.045

Bienville

71068 0.039 0.091 0.04 C 1.2 1.2 1.7 0.07 0.047

171016 0.039 0.09 0.04 C 1.2 1.2 1.7 0.07 0.04771008 0.041 0.096 0.043 C 1.2 1.2 1.7 0.07 0.04971028 0.043 0.1 0.044 C 1.2 1.2 1.7 0.07 0.052

Bossier71064 0.044 0.101 0.044 E 2.5 2.5 3.5 0.15 0.110

171006 0.041 0.096 0.042 E 2.5 2.5 3.5 0.15 0.10371051 0.039 0.091 0.04 E 2.5 2.5 3.5 0.14 0.098




Caddo71082 0.042 0.096 0.042 E 2.5 2.5 3.5 0.15 0.105

171107 0.04 0.092 0.041 E 2.5 2.5 3.5 0.14 0.100

71047 0.038 0.087 0.038 E 2.5 2.5 3.5 0.13 0.095 1

Calcasieu

70661 0.027 0.06 0.027 E 2.5 2.5 3.5 0.09 0.068

170665 0.026 0.058 0.026 E 2.5 2.5 3.5 0.09 0.065

70611 0.027 0.06 0.027 E 2.5 2.5 3.5 0.09 0.068

70607 0.026 0.057 0.026 E 2.5 2.5 3.5 0.09 0.065

Caldwell71418 0.042 0.098 0.044 E 2.5 2.5 3.5 0.15 0.105

171435 0.04 0.094 0.043 E 2.5 2.5 3.5 0.15 0.100

Cameron

70631 0.023 0.051 0.024 E*2 2.5 2.5 3.5 0.08 0.058

170643 0.023 0.05 0.024 E* 2.5 2.5 3.5 0.08 0.058

70630 0.025 0.056 0.026 E* 2.5 2.5 3.5 0.09 0.063

70645 0.024 0.054 0.025 E* 2.5 2.5 3.5 0.09 0.060

Catahoula71343 0.036 0.084 0.039 E* 2.5 2.5 3.5 0.14 0.090

171340 0.038 0.088 0.04 E* 2.5 2.5 3.5 0.14 0.095

71368 0.039 0.091 0.042 E* 2.5 2.5 3.5 0.15 0.098

Claiborne71038 0.049 0.114 0.048 C 1.2 1.2 1.7 0.08 0.059

171040 0.047 0.109 0.046 C 1.2 1.2 1.7 0.08 0.056

71003 0.045 0.104 0.045 C 1.2 1.2 1.7 0.08 0.054

Concordia71354 0.034 0.079 0.037 E*2 2.5 2.5 3.5 0.13 0.085

171334 0.037 0.086 0.04 E* 2.5 2.5 3.5 0.14 0.093

70753 0.031 0.071 0.033 E* 2.5 2.5 3.5 0.12 0.078




Desoto71063 0.036 0.083 0.037 C 1.2 1.2 1.7 0.06 0.043

171046 0.037 0.084 0.037 C 1.2 1.2 1.7 0.06 0.044

71052 0.037 0.084 0.037 C 1.2 1.2 1.7 0.06 0.044

East Baton Rouge

70791 0.031 0.069 0.032 E 2.5 2.5 3.5 0.11 0.078

170810 0.03 0.066 0.03 E 2.5 2.5 3.5 0.11 0.075

70815 0.03 0.067 0.031 E 2.5 2.5 3.5 0.11 0.075

East Carroll

71254 0.058 0.138 0.056 E*2 2.5 2.5 3.5 0.20 0.145

271286 0.054 0.13 0.053 E* 2.5 2.5 3.5 0.19 0.135

71276 0.052 0.124 0.051 E* 2.5 2.5 3.5 0.18 0.130

East Feliciana

70761 0.041 0.094 0.041 D 1.6 1.6 2.4 0.10 0.066

170722 0.032 0.072 0.033 D 1.6 1.6 2.4 0.08 0.051

70777 0.031 0.07 0.032 D 1.6 1.6 2.4 0.08 0.050

Evangeline70554 0.029 0.064 0.03 E 2.5 2.5 3.5 0.11 0.073

170586 0.029 0.065 0.031 E 2.5 2.5 3.5 0.11 0.073

Franklin71295 0.043 0.101 0.045 E 2.5 2.5 3.5 0.16 0.108

271336 0.041 0.096 0.044 E 2.5 2.5 3.5 0.15 0.103

71232 0.048 0.115 0.049 E 2.5 2.5 3.5 0.17 0.120

Grant

71432 0.037 0.085 0.039 D 1.6 1.6 2.4 0.09 0.059

171467 0.035 0.08 0.037 D 1.6 1.6 2.4 0.09 0.056

71454 0.035 0.081 0.037 D 1.6 1.6 2.4 0.09 0.056

71417 0.034 0.078 0.036 D 1.6 1.6 2.4 0.09 0.054

Iberia

70538 0.025 0.055 0.026 E*2 2.5 2.5 3.5 0.09 0.063

170560 0.026 0.057 0.027 E* 2.5 2.5 3.5 0.09 0.065

70563 0.026 0.058 0.027 E* 2.5 2.5 3.5 0.09 0.065




Iberville70788 0.029 0.063 0.029 E* 2.5 2.5 3.5 0.10 0.073

170740 0.029 0.065 0.03 E* 2.5 2.5 3.5 0.11 0.073

70764 0.029 0.064 0.029 E* 2.5 2.5 3.5 0.10 0.073

Jackson

71251 0.041 0.095 0.043 C 1.2 1.2 1.7 0.07 0.049

171226 0.042 0.099 0.044 C 1.2 1.2 1.7 0.07 0.050

71268 0.042 0.098 0.043 C 1.2 1.2 1.7 0.07 0.050

71238 0.044 0.103 0.045 C 1.2 1.2 1.7 0.08 0.053

Jefferson

70094 0.027 0.059 0.027 E*2 2.5 2.5 3.5 0.09 0.068

170072 0.026 0.058 0.027 E* 2.5 2.5 3.5 0.09 0.065

70036 0.026 0.054 0.026 E* 2.5 2.5 3.5 0.09 0.065

70067 0.025 0.055 0.026 E* 2.5 2.5 3.5 0.09 0.063

Jefferson Davis

70549 0.025 0.056 0.026 D 1.6 1.6 2.4 0.06 0.040

170591 0.026 0.058 0.027 D 1.6 1.6 2.4 0.06 0.042

70532 0.028 0.062 0.029 D 1.6 1.6 2.4 0.07 0.045

Lafayette70520 0.028 0.061 0.029 E*2 2.5 2.5 3.5 0.10 0.070

170592 0.026 0.058 0.027 E* 2.5 2.5 3.5 0.09 0.065

70529 0.027 0.059 0.028 E* 2.5 2.5 3.5 0.10 0.068

Lafourche70301 0.026 0.057 0.026 E* 2.5 2.5 3.5 0.09 0.065

170374 0.024 0.053 0.025 E* 2.5 2.5 3.5 0.09 0.060

70357 0.022 0.048 0.024 E* 2.5 2.5 3.5 0.08 0.055

LaSalle71371 0.036 0.083 0.038 E 2.5 2.5 3.5 0.13 0.090

171465 0.039 0.091 0.041 E 2.5 2.5 3.5 0.14 0.098

71342 0.035 0.082 0.038 E 2.5 2.5 3.5 0.13 0.088

Lincoln71270 0.045 0.106 0.046 C 1.2 1.2 1.7 0.08 0.054

171275 0.044 0.104 0.045 C 1.2 1.2 1.7 0.08 0.053

71235 0.048 0.113 0.048 C 1.2 1.2 1.7 0.08 0.058




Livingston70785 0.031 0.068 0.031 E 2.5 2.5 3.5 0.11 0.078

170449 0.029 0.065 0.03 E 2.5 2.5 3.5 0.11 0.073

70754 0.03 0.067 0.031 E 2.5 2.5 3.5 0.11 0.075

Madison71282 0.049 0.116 0.049 E*2 2.5 2.5 3.5 0.17 0.123

271232 0.048 0.115 0.049 E* 2.5 2.5 3.5 0.17 0.120

Morehouse71264 0.05 0.118 0.05 E 2.5 2.5 3.5 0.18 0.125

271220 0.054 0.129 0.053 E 2.5 2.5 3.5 0.19 0.135

71250 0.061 0.144 0.057 E 2.5 2.5 3.5 0.20 0.153

Natchitoches71070 0.038 0.088 0.04 E 2.5 2.5 3.5 0.14 0.095

171457 0.036 0.082 0.037 E 2.5 2.5 3.5 0.13 0.090

71468 0.034 0.078 0.035 E 2.5 2.5 3.5 0.12 0.085

Orleans70129 0.028 0.06 0.028 E*2 2.5 2.5 3.5 0.10 0.070

170131 0.027 0.058 0.027 E* 2.5 2.5 3.5 0.09 0.068

70124 0.027 0.06 0.028 E* 2.5 2.5 3.5 0.10 0.068

Ouachita

71203 0.048 0.114 0.049 D 1.6 1.6 2.4 0.12 0.077

1

71202 0.046 0.109 0.047 D 1.6 1.6 2.4 0.11 0.074

71292 0.045 0.107 0.047 D 1.6 1.6 2.4 0.11 0.072

71225 0.046 0.109 0.047 D 1.6 1.6 2.4 0.11 0.074

71291 0.047 0.111 0.048 D 1.6 1.6 2.4 0.12 0.075

Plaquemines70083 0.024 0.051 0.025 E*2 2.5 2.5 3.5 0.09 0.060

170037 0.026 0.057 0.027 E* 2.5 2.5 3.5 0.09 0.065

70091 0.021 0.045 0.023 E* 2.5 2.5 3.5 0.08 0.053




Pointe Coupee

70715 0.031 0.07 0.033 E* 2.5 2.5 3.5 0.12 0.078

170762 0.03 0.068 0.031 E* 2.5 2.5 3.5 0.11 0.075

70753 0.031 0.071 0.033 E* 2.5 2.5 3.5 0.12 0.078

Rapides

71328 0.033 0.077 0.036 E 2.5 2.5 3.5 0.13 0.083

171430 0.031 0.07 0.033 E 2.5 2.5 3.5 0.12 0.078

71409 0.033 0.074 0.034 E 2.5 2.5 3.5 0.12 0.083

71360 0.033 0.076 0.035 E 2.5 2.5 3.5 0.12 0.083

Red River71019 0.037 0.086 0.038 E 2.5 2.5 3.5 0.13 0.093

171068 0.039 0.091 0.04 E 2.5 2.5 3.5 0.14 0.098

Richland

71269 0.048 0.113 0.048 E 2.5 2.5 3.5 0.17 0.120

271259 0.044 0.104 0.046 E 2.5 2.5 3.5 0.16 0.110

71232 0.048 0.115 0.049 E 2.5 2.5 3.5 0.17 0.120

Sabine

71429 0.033 0.075 0.033 C 1.2 1.2 1.7 0.06 0.040

171419 0.036 0.081 0.035 C 1.2 1.2 1.7 0.06 0.043

71449 0.035 0.077 0.034 C 1.2 1.2 1.7 0.06 0.042

St. Bernard70085 0.026 0.057 0.027 E*2 2.5 2.5 3.5 0.09 0.065

170043 0.027 0.059 0.026 E* 2.5 2.5 3.5 0.09 0.068

St. Charles

70070 0.027 0.059 0.027 E*2 2.5 2.5 3.5 0.09 0.068

170057 0.027 0.06 0.028 E* 2.5 2.5 3.5 0.10 0.068

70087 0.027 0.06 0.028 E* 2.5 2.5 3.5 0.10 0.068




St. Helena70441 0.032 0.073 0.034 D 1.6 1.6 2.4 0.08 0.051

170422 0.031 0.07 0.033 D 1.6 1.6 2.4 0.08 0.050

70453 0.031 0.07 0.032 D 1.6 1.6 2.4 0.08 0.050

St. James70090 0.027 0.06 0.028 E*2 2.5 2.5 3.5 0.10 0.068

170086 0.028 0.061 0.028 E* 2.5 2.5 3.5 0.10 0.070

70723 0.028 0.062 0.028 E* 2.5 2.5 3.5 0.10 0.070

St. John70068 0.028 0.062 0.028 E*2 2.5 2.5 3.5 0.10 0.070

170049 0.028 0.061 0.028 E* 2.5 2.5 3.5 0.10 0.070

70051 0.028 0.061 0.028 E* 2.5 2.5 3.5 0.10 0.070

St. Landry70358 0.021 0.045 0.023 E*2 2.5 2.5 3.5 0.08 0.053

170570 0.028 0.064 0.03 E* 2.5 2.5 3.5 0.11 0.070

70512 0.028 0.063 0.029 E* 2.5 2.5 3.5 0.10 0.070

St. Martin70582 0.027 0.06 0.028 E*2 2.5 2.5 3.5 0.10 0.068

170517 0.028 0.061 0.029 E* 2.5 2.5 3.5 0.10 0.070

St. Mary70538 0.025 0.055 0.026 E*2 2.5 2.5 3.5 0.09 0.063

170392 0.024 0.053 0.025 E* 2.5 2.5 3.5 0.09 0.060

70544 0.026 0.057 0.027 E* 2.5 2.5 3.5 0.09 0.065

St. Tammany

70461 0.029 0.064 0.03 E 2.5 2.5 3.5 0.11 0.073

170431 0.031 0.069 0.032 E 2.5 2.5 3.5 0.11 0.078

70447 0.03 0.066 0.031 E 2.5 2.5 3.5 0.11 0.075




Tangipahoa70454 0.03 0.067 0.031 D 1.6 1.6 2.4 0.07 0.048

170422 0.031 0.07 0.033 D 1.6 1.6 2.4 0.08 0.050

70444 0.032 0.073 0.034 D 1.6 1.6 2.4 0.08 0.051

Tensas71357 0.043 0.1 0.045 E*2 2.5 2.5 3.5 0.16 0.108

271366 0.04 0.095 0.043 E* 2.5 2.5 3.5 0.15 0.100

71375 0.039 0.091 0.042 E* 2.5 2.5 3.5 0.15 0.098

Terrebonne70397 0.022 0.049 0.024 E*2 2.5 2.5 3.5 0.08 0.055

170356 0.024 0.053 0.025 E* 2.5 2.5 3.5 0.09 0.060

70344 0.023 0.049 0.024 E* 2.5 2.5 3.5 0.08 0.058

Union71277 0.054 0.127 0.051 C 1.2 1.2 1.7 0.09 0.065

171260 0.055 0.13 0.053 C 1.2 1.2 1.7 0.09 0.066

71234 0.048 0.113 0.048 C 1.2 1.2 1.7 0.08 0.058

Vermilion70548 0.025 0.056 0.026 E*2 2.5 2.5 3.5 0.09 0.063

170510 0.025 0.056 0.026 E* 2.5 2.5 3.5 0.09 0.063

70548 0.025 0.056 0.026 E* 2.5 2.5 3.5 0.09 0.063

Vernon71446 0.032 0.071 0.032 C 1.2 1.2 1.7 0.05 0.038

170656 0.03 0.068 0.031 C 1.2 1.2 1.7 0.05 0.036

71403 0.033 0.073 0.033 C 1.2 1.2 1.7 0.06 0.040

Washington70438 0.032 0.072 0.034 D 1.6 1.6 2.4 0.08 0.051

170427 0.032 0.071 0.033 D 1.6 1.6 2.4 0.08 0.051

70426 0.033 0.074 0.035 D 1.6 1.6 2.4 0.08 0.053




Webster71072 0.047 0.109 0.046 D 1.6 1.6 2.4 0.11 0.075

171073 0.042 0.097 0.043 D 1.6 1.6 2.4 0.10 0.067

Webster 71055 0.043 0.1 0.044 D 1.6 1.6 2.4 0.11 0.069 1

West Baton Rouge

70767 0.03 0.067 0.031 E*2 2.5 2.5 3.5 0.11 0.075 1

West Carroll

71263 0.059 0.14 0.056 E 2.5 2.5 3.5 0.20 0.148

271266 0.054 0.128 0.053 E 2.5 2.5 3.5 0.19 0.135

71237 0.052 0.124 0.051 E 2.5 2.5 3.5 0.18 0.130

West Feliciana

70775 0.031 0.071 0.033 D 1.6 1.6 2.4 0.08 0.050 1

Winn

71422 0.039 0.092 0.041 C 1.2 1.2 1.7 0.07 0.047

171473 0.04 0.093 0.042 C 1.2 1.2 1.7 0.07 0.048

71483 0.038 0.088 0.039 C 1.2 1.2 1.7 0.07 0.046


The following Parishes are designated Seismic Zone 2:

East Carroll FranklinMadisonMorehouseRichlandTensasWest Carroll

All bridges located in these parishes shall be designed using the provisions under Extreme I.


Seismic Zone Classification Map


Summary:

The structural analysis and design for theearthquake loads are specified in LRFDspecification as for four seismic zones, i.e.seismic zone 1, zone 2, zone 3 and zone 4.

Bridges in LA State shall be designed forseismic zone 1 and zone 2.


Summary:

LA Bridges in seismic zone 1 need not beanalyzed for seismic loads , regardless of theiroperational classification and geometry exceptfor the minimum requirements as specified inArticles 3.10.9 and A4.7.4.4.


Summary:

Bridges in Seismic Zone 2 shall be analyzedand designed in accordance with theminimum requirements specified in LRFDdesign specification, and the latest versionof “AASHTO guide specifications for LRFDseismic bridge design”


Summary:

The structural analysis and structural design,respectively, shall be taken into consideration forbridges located in seismic zone 2.

Bridges shall be analyzed and designed inaccordance with the minimum requirementsspecified in LRFD design specification, and thelatest version of “AASHTO guide specificationsfor LRFD seismic bridge design”


Summary:

The SEISMIC design requirements of Article 5.10.11.4 (for Seismic Zones 3 and 4) shall be taken to apply to bridges in Seismic Zone 2 except that the area of longitudinal reinforcement shall not be less than 0.01 or more than 0.06 times the gross cross-section area, Ag.


Table 4.7.4.3.1-1—Minimum Analysis Requirements for Seismic Effects

Seismic Zone

Single-Span

Bridges

Multispan BridgesOther Bridges Essential Bridges Critical Bridges

regular irregular regular irregular regular irregular1 No seismic

analysis required

* * * * * *

2 SM/UL SM SM/UL MM MM MM

* = no seismic analysis required UL = uniform load elastic methodSM = single-mode elastic method MM = multimode elastic method

Regularity is a function of the number of spans and the distribution of weight and stiffness.

Regular bridges have less than seven spans; no abrupt or unusualchanges in weight, stiffness, or geometry; and no large changes in these parameters from span to span or support-to-support.


In general, the upper boundary for Zone 2 in the current edition is significantly higher than in the previous edition due to the increase in the return period for the design earthquake.


Thank You

new seismic design requirements in louisiananew seismic design ... established knowledge about the...

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