charles thiel - Academia.edu (original) (raw)

Papers by charles thiel

The Race to Seismic Safety is a comprehensive report to the director of the California Department... more The Race to Seismic Safety is a comprehensive report to the director of the California Department of Transportation (Caltrans) justifying the urgent need for the California legislature to institutionalize practices that will lead to adequate seismic performance of the state's transportation system. The report, prepared by the Caltrans Seismic Advisory Board (SAB), identifies a disturbing trend to de-emphasize seismic safety, as evidenced by the passage of Assembly Bill 2996 in 2002. This trend, if continued under the current administration, increases the probability that California will lose its race to achieve a safe transportation system before the next damaging earthquake, with possible catastrophic implications for life safety and the economy of California.

... Leadership & Management: Awards; Career Resources; Contract Documents; Diversity; Ethics;... more ... Leadership & Management: Awards; Career Resources; Contract Documents; Diversity; Ethics; Industry Outlook; Leadship Resources; Licensure; ... Lifelines, Seismic Hazards and Public Policy. by Charles Conrad Thiel, Jr. , M.ASCE pp. ...

Structural Design of Tall and Special Buildings, Nov 6, 2018

How long can a seismically deficient building be used until the seismic risk becomes too high to ... more How long can a seismically deficient building be used until the seismic risk becomes too high to be acceptable? A model interim use plan is developed with requirements to abandon the building if retrofit is not completed in the use period. Acceptable seismic performance is keyed to American Society of Civil Engineers (ASCE) 41 levels. The acceptable occupancy or use period is limited to that which results in the same probability of performance as stated for an ASCE 7-16-compliant building, except that the total risk in the use period is due to all possible earthquakes impacting the site, not just the maximum considered earthquake. The Thiel-Zsutty damage model is used to determine the probabilities for assigned threshold ranges where unacceptable performance can occur. Other response prediction models can be used if they provide an annual probability of a given performance level exceedance. Example applications are given for both marginally and highly deficient buildings located at 17 national sites in high and moderate seismic hazard regions and include ASCE 7 Risk Class I-IV buildings. This approach may be applied to any risk decision-making issue for which there is an annual probability of damage exceedance.

Bulletin of the Seismological Society of America, Oct 1, 1991

A Board of Inquiry was appointed by the Governor of California to investigate the damage, particu... more A Board of Inquiry was appointed by the Governor of California to investigate the damage, particularly to bridges and freeway structures, caused by the 1989 Loma Prieta earthquake. The Governor wanted to know not only what happened, but how to prevent such destruction in the future. The Board identified three essential challenges that must be addressed by the citizens of California, if they expect a future adequately safe from earthquakes: (1) ensure that earthquake risks posed by new construction are acceptable; (2) identify and correct unacceptable seismic safety conditions in existing structures; and (3) develop and implement actions that foster the rapid, effective, and economic response to and recovery from damaging earthquakes. The Governor issued an Executive Order implementing the principal Board recommendations that all state-owned and -operated structures are to be seismically safe and that important structures are to maintain their function after earthquakes. The Seismic Safety Commission has evaluated the response of state agencies to the Order and found performance generally to be good, but variable. Inadequate funding is the most serious and the most difficult for the agencies to address internally, as are legislative capital budgeting processes that are cumbersome. Agencies were encouraged to identify single administrators responsible for seismic safety to assure management accountability, rather than the generally diffuse responsibility found in most agencies. The Board, Governor, and Commission all concluded that, while much progress has been made during the past two decades in reducing earthquake risks, much more awaits doing. More aggressive efforts to mitigate the consequences of future, certain earthquakes are needed if one of the most fundamental of responsibilities of government is to be fulfilled—to provide for the public safety.

Structural Design of Tall Buildings, Dec 1, 1999

... The risks in doing so appear to the author to be at most modest. ACKNOWLEDG EMENTS Dario Rosi... more ... The risks in doing so appear to the author to be at most modest. ACKNOWLEDG EMENTS Dario Rosidi, Woodward-Clyde Consultants, Oakland, provided the ground motion estimates for which these analyses were completed. ...

Earthquake Spectra, May 1, 1989

Earthquake Spectra, Nov 1, 1987

A simple Markov distribution relates the probability of occurrence of five discrete damage states... more A simple Markov distribution relates the probability of occurrence of five discrete damage states for a specific building type in an earthquake. Within the model the damage distribution depends on parameters that represent the building's structural system, the matching of the site and building periods, and the site materials, and the site's acceleration. The constants in the model were determined using a maximum likelihood formulation and damage observations for a series of California and Chinese earthquakes. Model predictions of damage distributions agree well with reserved damage data not used in determining the constants. A maximum likelihood method allows determination of ground motion, attenuation, and/or earthquake moment magnitude from observations of damage for different types of structures located at diverse sites. A simple relationship exists for average damage estimate that closely matches historical observations.

Structural Design of Tall Buildings, Sep 1, 1997

An approach to the evaluation of the damageability of buildings and the determination of probable... more An approach to the evaluation of the damageability of buildings and the determination of probable maximum loss (PML) values is presented and applied to welded steel moment frame buildings. PML is de®ned as the loss that has a given (usually 10%) probability of exceedance in a speci®ed number of years from earthquake ground shaking. A Markov Model developed is used in a Monte Carlo simulation to determine damage statistics, from which PML values are determined. Four sites within the Los Angeles area are considered, as are a range of building damageabilities from very low to very high. Speci®c assessments are made for welded steel moment frame buildings representative of the post-Northridge understanding of damageability. PML values are shown to be very sensitive to the probability of loss exceedance, the time period considered, the number of buildings in the portfolio, and the lower bounds of earthquake magnitude and ground motions considered. The number of buildings considered in the PML assessment is shown to be very important as a means of reducing PML values. The use of MMI ground motion characterization is assessed and found to be wanting. A comparison of PML results with other damageability measures (both average and 10% exceedance) for four sites, including different ground motions and earthquakes, and a maximum probable loss associated with the closest serious earthquake, indicates that these other measures are not good estimators of the full probabilistic PML that considers in a consistent manner both site ground motion and building performance uncertainty.

Earthquake Spectra, Nov 1, 1995

Earthquake Spectra, Nov 1, 1984

Structural Design of Tall and Special Buildings, Jun 9, 2017

SummaryThe revised Thiel–Zsutty model predicts the probability distribution function for earthqua... more SummaryThe revised Thiel–Zsutty model predicts the probability distribution function for earthquake damageability of a building as a function of peak ground acceleration and parameters that represent the site soils, building damageability, and uncertainty of the basis for parameter selection. Guidance is provided on how to assign revised Thiel–Zsutty parameters and for procedures to determine these parameters for a given building and site. Parameter base values are given for ASCE 7 structural systems and soil classes. The model includes representation of the uncertainty in the parameter evaluations according to level and quality of investigation through an uncertainty factor. It is keyed to ASTM investigation levels and determined by either a constructive or descriptive approach from the characteristics of the building and its design and construction. Procedures are developed for cases where the damageability factor changes as the buildings or site's response changes its character as the level of excitation increases. Guidance is provided on how to incorporate nonlinear time history analyses for performance‐based design of tall buildings and other structures.

Structural Design of Tall and Special Buildings, Mar 24, 2017

The Thiel-Zsutty (TZ) model predicts mean and the probability distribution function for earthquak... more The Thiel-Zsutty (TZ) model predicts mean and the probability distribution function for earthquake damageability of building as a function of peak ground acceleration. ATC-13-1 provides an alternate damageability model based on modified Mercalli intensity characterization of ground motion and a beta distribution function for selected building types. This paper provides a reconciliation of the TZ and Applied Technology Council (ATC) methods. It is shown that the beta distribution can provide a continuous representation of the step-wise TZ Markov distribution function. When the TZ model uses a compression factor for the standard deviation to represent the degree of uncertainty in the parameters, then the TZ results are found to be consistent with the ATC-13-1 distribution function for a specific compression factor of 0.40. This paper provides a new, simply applicable method to determine the damage distribution function for a given site, building type, and site conditions; using a beta distribution and allowing inclusion of the degree of confidence the assessor has in the determination of the parameters. New equations are provided to estimate the mean, standard deviation, and upper confidence limit of the damage ratio.

Structural Design of Tall and Special Buildings, Oct 15, 2010

Two common scenario loss ratios are used when calculating Probable Maximum Losses from earthquake... more Two common scenario loss ratios are used when calculating Probable Maximum Losses from earthquakes: Scenario Expected Loss (SEL) and Scenario Upper Loss (SUL). Analyses of seismic loss ratios prepared by fi ve seismic consulting fi rms, four loan pools securitized in the capital markets, two very large loans with many properties, two large hospitality portfolios and a general account portfolio indicate that use of SUL rather than SEL would yield signifi cantly larger numbers of loans with loss ratios in excess of 20%. When using SEL, the percentage of loans in the four large pools exceeding a 20% loss ratio was 3.8%. When SUL was used on this same data set, 47.8% of these properties had SUL values above 20%. Common industry practice has been to use SEL. Some of the implications of tightening seismic underwriting standards to apply a 20% threshold to the SUL, rather than SEL, may include: lower loan production, properties may lose value, properties may be costlier and more diffi cult to fi nance, existing loan portfolios may appear more seismically risky, and demand for insurance and seismic retrofi t could go up. Equally undesirable effects could be that seismic consultants and lenders who do more rigorous analysis will be less competitive than those who do not.

Structural Design of Tall Buildings, 2002

Earthquake vulnerability is an important financial issue in evaluating the acceptability of a pro... more Earthquake vulnerability is an important financial issue in evaluating the acceptability of a property as a security for a loan or for an equity position. Such analyses are usually performed as part of the due diligence assessment of the property. Probable loss (PL) and scenario loss (SL), for both design basis and maximum capable earthquakes, were assessed to determine their utility in damageability analyses. Evaluations were made for a range of building damageabilities and for 14 sites throughout the United States that are representative of seismic hazard from very high to low. Portfolios from one to 16 buildings are considered. The analysis indicates that none of the damageability criteria is sufficient to distinguish between good and bad buildings to be securities for loans or to be good risks for equity investment for general use throughout the United States. Scenario upper loss (SUL) and probable loss (PL) values are consistently very stringent criteria for individual buildings in moderate-risk and high-risk regions, while scenario expected loss (SEL) values are too lenient in moderate risk areas. PL and SUL criteria are much too stringent at the 20% threshold level to be used generally, except for a group of well-designed buildings. They can be acceptable if threshold values for acceptance are set to be above 20%. The SEL criterion is evaluated as not adequate to discriminate between good and bad damageability buildings by itself. It can work well in combination with a stability criterion so that buildings with poor predicted earthquake performance are eliminated based on stability, not damageability. It is recommended that combined criteria be used for fiduciary evaluation that includes both an assessment of the stability of the buildings and a damageability assessment to achieve a balanced, consistent evaluation of the suitability of the buildings as securities or as investments. Four alternative acceptance criteria are recommended for due diligence assessments. It is recommended that all due diligence reports include evaluations of scenario and probable losses for each building and the group so that they can enter into the decision process for the property.

Earthquake Spectra, Feb 1, 1987

Earthquake Spectra, Oct 8, 2021

Seismic risk evaluation studies for real estate portfolios conducted by technical professionals (... more Seismic risk evaluation studies for real estate portfolios conducted by technical professionals (often Civil and Structural Engineers) have become increasingly desirable and common in financial decisions. In this article, we develop a series of risk measures and ratings based on common outcomes from probabilistic portfolio seismic risk assessments. We first define two portfolio risk metrics: Portfolio Expected Loss (PELα) and Portfolio Upper Loss (PULα), where “α” is the annual exceedance probability, or the corresponding return period (“1/α”). PULα/PELα ratio characterizes the uncertainty in estimated portfolio risks which results from the uncertainty in seismic performance of the individual assets. Three uncertainty levels are defined, namely, low, medium, and high, based on the PULα/PELα. We then develop an asset risk metric, called Tail Contribution Index (TCIα), that characterizes the contribution of individual assets to the portfolio losses that fall within the high-consequence “tail” of the portfolio loss distribution. To describe the overall engineering efforts of a portfolio seismic risk study, we develop a portfolio risk metric, called Portfolio Level of Investigation (PLIα), that characterizes the effective level of engineering investigation. Three investigation levels are defined: low ( desktop), medium ( semi-engineered), and high ( engineered), based on the PLIα. Finally, based on the combination of uncertainty level and investigation level, we develop a rating scheme by which the quality (Qα) of a portfolio seismic risk study is characterized. Five quality levels are defined: very poor, poor, fair, good, and very good. These risk indices and ratings can help stakeholders and technical professionals better diagnose and communicate portfolio seismic risks, scope adequate studies, effectively utilize valuable resources, and base financial decisions on risk assessment results that have the desired reliability.

Risks, Jul 6, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY