IMPROVING PERFORMANCE TO REDUCE SEISMIC RISK 5 

5.1 INTRODUCTION 

Improving performance to reduce seismic risk is a multi-faceted issue that 
requires consideration of a broad range of factors. Previous chapters in this 
document have introduced and described the overarching concept of seismic 
risk management (Chapter 2) and two of the fundamental factors affecting 
improved seismic performance: consideration of the seismic hazards affecting 
the site (Chapter 3); and consideration of the desired seismic performance of 
structural and nonstructural components for the range of earthquakes of 
concern (Chapter 4).  

This chapter identifies and addresses related seismic design issues that are 
fundamentally important to improved seismic performance, regardless of the 
occupancy type: 

selection of the structural materials and systems (Section 5.2); 

selection of the architectural/structural configuration (Section 
5.3);

consideration of the expected performance of nonstructural components, 
including ceilings, partitions, heating, ventilation, and air condition equipment 
(HVAC), piping and other utility systems, and cladding (Section 5.4); 

cost analysis, including consideration of both the benefits and costs of 
improved seismic performance (Sections 5.5 through 5.7); 

and quality control during the construction process (Section 5.8). 

Considerable attention is given to the quantification of benefits and costs of 
improved seismic performance, given the underlying importance of cost 
considerations.  Benefits include reduced direct capital losses and reduced 
indirect losses, which are related to the time that a given building is 
operationally out of service.  Cost issues are demonstrated through several 
means, including the use of (1) graphics showing the relationship between the 
cost of various options for improving seismic performance versus the resulting 
benefits; and (2) case studies demonstrating best practices in earthquake 
engineering. 

The Chapter concludes with a set of general recommendations for improving 
seismic performance during the seismic design and construction process, 
regardless of occupancy type.  The subsequent six chapters focus on seismic 
design and performance issues related to spe-cific occupancy types:  
commercial office buildings (Chapter 6): retail commercial facilities (Chapter 
7); light manufacturing facilities (Chapter 8); healthcare facilities (Chapter 9); 
local schools, kindergarten through grade 12 (Chapter 10); and higher 
education (university) facilities (Chapter 11). 



5.2	   SELECTION OF STRUCTURAL MATERIALS AND SYSTEMS 

An earthquake has no knowledge of building function, but uncovers 
weaknesses in the building that are the result of errors or deficiencies in its 
design and construction.  However, variations in design and construction will 
affect its response, perhaps significantly, and to the extent that these 
variations 
are determined by the occupancy, then each building type tends to have some 
unique seismic design determinants.  A building that uses a moment-frame 
structure will have a different ground motion response than a building that uses 
shear walls; the frame structure is more flexible, so it will experience lower 
earthquake forces, but it will deflect more than the shear wall structure, and 
this 
increased motion may cause more damage to nonstructural components such 
as partitions and ceilings. The shear wall building will be much stiffer but this 
will attract more force: the building will deflect less but will experience higher 
accelerations and this will affect acceleration-sensitive components such as 
air conditioning equipment and heavy tanks. 

These structural and nonstructural system characteristics can be deduced 
from the information in the seismic code, but the code is not a design guide 
and gives no direct guidance on the different performance characteristics of 
available systems or how to select an appropriate structural system for a 
specific site or building type. 

Table 5-1 illustrates the seismic performance of common structural systems, 
both old and new, and gives some guidance as to the applicability of systems 
and critical design characteristics for good performance. The different structural 
performance characteristics mean that their selection must be matched to the 
specific building type and its architecture.  Table 5-1 summarizes a great deal 
of information and is intended only to illustrate the point that structural 
systems 
vary in their performance.  The table is not intended as the definitive tool for 
system selection; this requires extensive knowledge, experience and analysis. 
Table 5-2 shows structural system selections that are appropriate for different 
site conditions, for different occupancies and various building functions. For 
example, an important aspect of the building site is that a major structure must 
be "de-tuned," that is, designed such that its fundamental period differs 
sufficiently from that of the ground so that dangerous resonance and force 
amplification are not induced.  Thus, for a soft, long-period site; it is 
appropriate 
to use a rigid short period structural system; this need in turn must be related 
to other requirements of occupancy and function. 

Table 5-2 also illustrates that structures must be matched to the build-ing's 
use. For example, a concrete shear wall structure is appropriate for an 
apartment house because the strong cross walls are an economical way to 
provide the necessary seismic resistance and, at the same time, provide good 
acoustics between the apartments. While the purpose of Table 5-2 is to 
illustrate the way in which structural systems may be matched to the site 
condition and building design and use, the table is not intended as the 
definitive tool for system selection; this also requires extensive knowledge, 
experience, and analysis. 



5.3 SELECTION OF THE ARCHITECTURAL CONFIGURATION 

The architectural configuration-the building's size, proportions and three-
dimensional form-plays a large role in determining seismic performance.  
This is because the configuration largely determines the distribution of 
earthquake forces, that is, the relative size and nature of the forces as they 
work 
their way through the building.  A good configuration will provide for a balanced 
force distribution, both in plan and section, so that the earthquake forces are 
carried directly and easily back to the foundations. A poor configuration results 
in stress concentrations and torsion, which at their worst are dangerous. 

Configuration problems have long been identified, primarily as the result of 
extensive observation of building performance in earthquakes. However, many 
of the problem configurations arise because they are useful and efficient in 
supporting the functional needs of the building or accommodating site 
constraints.  The design task is to create configuration alternatives that satisfy 
both the architectural needs and provide for structural safety and economy. This 
requires that the architect and engineer must cooperate from the outset of the 
design process: first to arrive at an appropriate structural system to satisfy 
building needs, and then to negotiate detailed design alternatives that avoid, or 
reduce, the impact of potential problem configurations. 

Seismic codes now have provisions intended to deal with configuration 
problems.  However, the code approach is to accept the problems and attempt 
to solve them either by increasing design forces, or requiring a more 
sophisticated analysis.  Neither of these approaches is satisfactory, for they do 
not remove the problem.  In addition, many of the code provisions apply only to 
buildings that are five stories or over 65 feet in height, which leaves a large 
number of buildings unregulated by the code.   The problem can only be solved 
by design and not by a prescriptive code. 

Design solutions for a soft first story condition that the architect and engineer 
might explore together include (see Figure 5-1): 

The architectural implications of eliminating it (which solves the 
structural problem);

Alternative framing designs, such as increasing the number of columns 
or increasing the system stiffness by changing the design, to  alleviate the 
stiffness discrepancy between the first and adjacent floors; and 

Adding bracing at the end of line of columns (if the site constraints 
permit this). 

A more general problem is the increasing unpredictability of building response 
as the architectural/structural configuration increasingly deviates from an ideal 
symmetrical form.  This has serious implications for Performance Based 
Design, which depends for its effectiveness on the ability of the engineer to 
predict structural performance. 

Tables 5-3 and 5-4 illustrate the above points by identifying the common 
configuration problems- termed "irregularities" that are dealt with in the seismic 
code. These are classified as vertical or plan irregularities.  The tables show a 
diagram of each condition, illustrates the failure pattern and describes its 
effects.   The designations and numbers of the conditions are identical to the 
code: the diagrams are not contained in the code but are interpretations of the 
descriptions of each condition that the code defines. 




5.4 	CONSIDERATION OF NONSTRUCTURAL COMPONENT 
PERFORMANCE 

As discussed in Section 4.2, the majority of the damage that has resulted in 
building closure following recent U.S. earthquakes has been the result of 
damage to nonstructural components and systems. A building designed to 
current seismic regulations may perform well structurally in a moderate 
earthquake, but be rendered nonfunctional due to non-structural damage. 

Nonstructural components may also, however, influence structural per-
formance in response to ground shaking.  Structural analysis to meet code 
requirements assumes a bare structure. Nonstructural components that are 
attached to the structure, and heavy contents, depending on their location, may 
introduce torsional forces.  Characteristic examples of structural/nonstructural 
interaction are as follows: 

Heavy masonry partitions that are rigidly attached to columns and under 
floor slabs, can, if asymmetrically located, introduce localized stiffness and 
create stress concentrations and torsional forces. A particular form of this 
condition, that has caused significant structural damage, is when short column 
conditions are created by the insertion of partial masonry walls between 
columns.  The addition of such partial walls after the building completion is 
often treated as a minor remodel that is not seen to require engineering 
analysis. The result is that the shortened columns have high relative stiffness, 
attract a large percentage of the earthquake forces, and fail (Figure 5-2). 

In smaller buildings, stairs can act as bracing members between
floors, introducing torsion; the solution is to detach the stair from 
the floor slab at one end to allow free structural movement.

In storage areas or library stacks, heavy storage items can introduce 
torsion into a structure.  The structure may have been calculated to
accommodate the maximum dead load but consideration be lack-
ing for the effect of nonsymmetric loading over time as, for exam-
ple, when library books are acquired (Figure 5-3).



5.5 QUANTIFYING THE BENEFITS OF IMPROVED PERFORMANCE 

The benefits of improved performance are the reduced losses resulting from 
improved performance.  These reduced losses include not only the reduction in 
capital losses (as described below), but also the reduction in financial impacts 
resulting from the loss of operations. 

The benefits of improved earthquake performance of a building are quantified 
differently by the various types of building owners and users. For example, an 
owner occupant, an owner of a tenant-occupied building, and a tenant will all 
have different priorities and views regarding the cost-benefit trade-offs 
associated with improved earthquake performance of the building. 

From the point of view of an owner occupant, earthquake performance of a 
building can be quantified in terms of reducing the probability of: 

deaths and injuries in and around the building caused by an earthquake, 
and the resultant liability; 

collapse of the building or damage to the building that reduces the 
building's value; 

disruption of building services (HVAC, plumbing, electrical) and 
the resultant loss of use of the building or portions of it;

damage to building contents such as furniture, files, and inventory; and 

disruption of building operation and business as a result of the above. From the 
point of view of an owner of a tenant-occupied building, earthquake performance of 
a building can be quantified in terms of reducing 
the probability of: 

deaths and injuries in and around the building caused by an earthquake, 
and the resultant liability; 

collapse of the building or damage to the building that reduces the 
building's value; and 

disruption of building services (HVAC, plumbing, electrical) and 
the resultant loss of use of the building or portions of it (tenant 
business interruption).


From the point of view of a tenant who is not the owner, earthquake 
performance of a building can be quantified in terms of reducing the probability 
of:

disruption of building services (e.g., HVAC, plumbing, electrical) 
and the resultant loss of use of the building or parts of it;

damage to building contents such as furniture, files, and contents; and 

disruption of building operation and business as a result of the above. 




Quantifying Expected Capital Losses

Capital losses consist of the cost of replacing or repairing earthquake-
damaged structural and nonstructural components as well as damaged 
building contents. When quantifying capital value of damaged building 
components and contents, the first distinction that needs to be made is 
between the depreciated value of an asset, its market value, and its 
replacement cost.  The assumption is generally that damaged capital will be 
replaced.  If a 50-year-old building or piece of equipment is damaged to the 
extent that it is a total loss, it is unlikely that an owner can have a 
replacement 
building constructed or purchase a new piece of equipment for the same price 
as the original cost, nor for the depreciated value of the building or equipment 
(which may be very low, or zero). One may purchase a replacement building or 
piece of equipment that is 50 years old.  Still, the price of that building or 
equip-
ment will be based not on the depreciated value, but on the current market 
value of the asset. When the cost of losing an asset is evaluated, the owner 
must therefore determine what the cost to replace the asset will be, whether it 
is new or used. 

An owner can use various means to estimate the replacement cost of a 
building or its contents.  Realtors, manufacturers, engineers, and other 
specialists can research market conditions to estimate costs.  If the owner has 
a large number of facilities or buildings, he/she may have a database of recent 
capital projects from which to draw information. 

If structural and nonstructural building elements suffer less than total
loss in an earthquake, they can often be repaired without being
replaced.  Theoretically, one would never spend more than the replacement 
cost of the building to repair structural and nonstructural damage.  Practically, 
most owners consider the limit of repair costs to be on the order of 40 to 60 
percent of the replacement cost.  The older the building or equipment, typically 
the lower the threshold.  The reasoning is that if a building or piece of 
equipment is old and outdated, repairing it leaves the owner with something 
that, although functional, is still old and possibly outdated. 

Owners may have other constraints which raise or lower this threshold.  If short 
on cash or credit, an owner may have no choice but to repair a heavily 
damaged building rather than replace it.  If the operations within the building 
are so valuable that losses from down time far exceed the building's 
replacement cost, then even if very expensive repairs can be done more quickly 
than replacement, the threshold of repairable damage may also be high.  On 
the other hand, if an owner has been looking to get rid of an old, poorly 
configured, structure even
small amounts of damage may provide a convenient excuse to replace
the building.

It should be clear that unit repair costs are rarely equal to the unit costs of 
new 
construction.  The cost of building partition walls in a new building, for 
example, 
may be on the order of five dollars per square foot.  Repairing heavily damaged 
partition walls may cost more than twice this amount.  Removing and replacing 
a damaged steel brace within a building may cost several times the cost of 
installing the brace in a new building. 

A key to estimating the cost of repairing structural and nonstructural damage is 
understanding what the nature of the damage may look like. This is often 
defined as the "fragility" of the building system.  Fragility presents the 
likelihood 
of damage as a function of the forces or deformations imposed on the building. 
 Damage may be described in terms that include cracking or spalling of 
concrete elements; fracturing or buckling of steel beams, columns, or braces; 
glazing breakage; and partition cracking or failure. Estimating how much 
damage occurs at a specific stress or deformation has been and continues to 
be the subject of research.  Once estimates of the damage are made, 
contractors and cost estimators can provide valuable assistance to owners and the 
design
team in estimating repair costs.

Damage to contents and inventory is usually quantified in terms of the amount 
of each that needs to be replaced. In some cases, with very expensive 
equipment or inventory, one might consider repairing damage.  In most 
instances, however, damaged items are typically replaced.  Damage to non-
fixed items typically occurs as a result of high accelerations "flinging" items 
off 
shelves or overturning them. Earthquake-induced accelerations vary over the 
height of a building so that items in upper stories may be more prone to 
damage than at lower stories. Estimating the amount of damage to contents 
and inventory involves calculating the acceleration at each level and estimating 
the capacity of elements at each story to withstand these accelerations. 
Shelving should be evaluated as to its overturning capacity and the potential 
damage of items that are spilled. 

Contents such as desks and cabinets are fairly resilient to damage from 
sliding or falling, and are typically considered as losses only when they cannot 
be recovered because of substantial structural damage. Therefore, one might 
consider a threshold of structural damage (say when the building is 
condemned following an earthquake, or when it reaches its replacement 
threshold) at which point most of the contents are considered lost. 


Quantifying Loss of Operations 

Structural and nonstructural damage may require that a building's operations 
be curtailed or cease altogether for some period during repair or replacement.  
The loss of operations will have a direct effect on the revenue or "value" of the 
services or goods that the business produces. It will also, presumably, have a 
broader impact on its employees, on the customers that it serves, and possibly 
on the community or region as a whole.  Business interruption may also be a 
factor in how soon, if ever, the business can recover lost opportunities and 
markets. 

The primary impacts caused by loss of operations include: 

Direct loss of revenue or value; 

Indirect losses to employees, customers, and the community at 
large; and

Long term business losses. 


All three of these impacts are dependent on how long and to what extent the 
business is out of operation. This is usually a function of structural and 
nonstructural damage, and may also be a function of contents loss.  The 
impact of loss of operations on two facility types are demonstrated in the  two 
example case studies described on the following page. 
The loss of function of any single building is unlikely to cause devastating 
consequences to people in the affected region; nonetheless, these losses can 
be severe if the affected facilities are critical to community functions or the 
local 
or regional economy. Following are example situations where the loss of a 
critical facility can negatively affect the community as a whole or have far-
reaching consequences: 

In August, the only high school in a city is damaged to the point where 
it 
must be replaced. Where do the students go to school for the coming year or 
more while a new facility is designed and built? 

The only county hospital with a trauma center is rendered non-func-
tional during an event that causes dozens of life-threatening injuries
within the community.

A pharmaceutical manufacturing plant that produces a popular
drug for which the company owns the patent is destroyed in an 
earthquake.  How will patients continue to get the drug?

An automotive parts manufacturer that provides "just-in-time" sup-
plies to an automobile maker cannot function for three months.
How will this affect the automobile company's ability to produce 
cars and its ability to keep its employees busy?


It is almost impossible to put a dollar value on the cost of these losses 
because, like many other events, the repercussions can be difficult to 
completely define.  It is therefore unrealistic to develop a pure cost-benefit 
study equating additional dollars spent on better performance with savings in 
terms of these reduced indirect effects. 

One can, however, make comparative studies with respect to other types of risks 
and establish an equivalent value of 
tolerating them.  In any of the examples above, the building owner will likely 
have liability insurance to protect against claims that could have a devastating 
impact on the entity.  A private school might have a catastrophic insurance 
policy to protect against a student being killed in a sporting event; a public 
school may have locally- or state-granted legal protections.  A hospital certainly 
has malpractice insurance and an automotive plant will have worker's 
compensation insurance.  However, insurance policies all have limits on 
coverage. If losses exceed the coverage limit the result could be bankruptcy. 
Yet the owner in all cases makes a decision to limit coverage and therefore to 
accept the remaining risk of catastrophic loss. 

Considering the example of the school injury, if a family of an injured student 
wins a judgment exceeding the school's insurance policy, the school may have 
to declare bankruptcy and close its doors. The school may be able to avert this 
consequence if it buys additional insurance. However, at some point it makes 
the decision that it is not going to spend more in premiums and is willing to 
accept the risk of a catastrophic loss. The process to arrive at this limit may 
have been explicitly or implicitly thought out. Regardless, it can be used as a 
guide for making other decisions about risk management for earthquakes. The 
case study icon (see next page) illustrates this hypothetical situation. 
When determining the level of performance for which a building should be 
designed, an owner may want to consider involving those outside the business 
who will be indirectly affected by the potential loss of operations.  A community 
might be willing to contribute to the cost of a higher performance design of a 
school if it considers the value of having the building usable after an 
earthquake sufficiently high.  Similarly, an auto maker might contribute to the 
performance-based design of one of its parts suppliers if it considers an 
uninterrupted supply of parts crucial to its own operations. 


Social and Political Factors Affecting Seismic Risk Management
 
Emotion and politics are often important factors in the seismic risk 
management decision-making process. Parents of school children may say, 
"No price is too high to pay for the safety of my child."  Politicians or business 
leaders may proclaim, "We have a zero tolerance policy for placing the 
occupants of our buildings at risk." While well intended, these positions are not 
often achieved in practice.  

The concept of placing a quantified (dollar) value on the life or safety of each 
person is a controversial issue that impacts benefit-cost analysis.  This 
approach is implemented by comparing the value of saved lives (the benefit) to 
the cost of protecting those lives.  Political or emotional constraints often make 
this extremely difficult.  If an owner looks beyond life safety, however, and 
focuses on capital losses or down time, then it is practical and possibly 
necessary to quantify these losses in terms that can be compared directly to 
the costs to reduce them. The fact that most new U.S.-code-designed buildings 
are expected to provide life safety (for the range of earthquakes that may occur 
over the life of the building) renders the need to assign dollar values to human 
lives less imperative. 





5.6 COSTS OF IMPROVED PERFORMANCE 

Building owners incur costs to obtain specified levels of building performance. 
These costs are considered "first costs" if incurred at the time of building 
design and construction or purchase.  They are considered "operating costs" if 
incurred over the period of use of the building. 

It should be noted that the period of use of a building by its owner might differ 
from the life of the building. The life of a building may be 60 years or more, 
while the owner's use could be much shorter. When considering societal costs 
of a building, for example energy use, soci-ety's interest in operating costs are 
spread over the life of the building, regardless of owner turnover.  The life of 
the 
building is also of interest in the operating cost considerations of certain types 
of owners, particularly institutional owners such as schools and universities.  
However, for most commercial owners considering making an investment in a 
building, operating costs are of interest only over the period that the owner 
anticipates owning the building. 

First Costs 

The following are typical of first costs: 

The costs of site selection, including the cost of physical and eco-
nomic analysis of alternative sites.

The costs of planning and programming a new building, including the 
costs of consultants. 

The costs of architectural and engineering design and construction 
management, in the case of the construction of a new building, or 
the transaction costs (e.g., inspection and appraisal), in the case of the 
acquisition of an existing building. 


The disruption of operations resulting from the move from a cur
rently used building to a new building. Except for the last item, there is 
generally 
a direct relationship between cost and building performance (including seismic 
performance) - a higher first cost investment typically results in improved 
performance. 

Operating cost analyses often categorize the costs of construction or purchase 
as first costs. This is short sighted in most cases, since these costs are 
usually financed through mortgages or bonds, which converts them into 
continuous operating costs. 


Operating Costs 

The following are typical operating costs: 

Operation and maintenance of the building, including costs of 
earthquake response and recovery.

Replacement of building components and systems, including the cost of 
disruption of operation related to these activities, both of which can be 
annualized if converted to a payment into a replacement reserve fund. 

Changing the building to accommodate new functions or technology, 
and the disruption of operation resulting from such activities (which is 
analogous to churn rate). 

Insuring the building. Higher costs in this category may improve 
building 
performance by reducing unrecoverable losses or they may be inversely related 
to it, depending on insurance company underwriting practices. 

Building and contents damage resulting from unpredictable events, 
such as natural and man-made disasters, which can be expressed as a 
probability of incurring an annual cost. 

Disruption of operation due to building damage resulting from 
unpredictable events, which can be also expressed as a probability of incurring 
an annual cost. 

Liability for deaths and injuries from building damage resulting 
from unpredictable events.




The Relationship Between Cost and Performance 

An advantage of performance-based design is that it provides a means for the 
design team to create a relationship between construction cost and 
performance.  Traditionally (i.e., using existing seismic codes for new building 
design), to achieve better performance an engineer might simply increase the 
importance (I) factor from 1.0 to 1.25, thereby raising the design seismic forces 
by 25%. This may make a building perform better; however, the benefit is not 
easily quantifiable, even if the cost in increased steel tonnage or concrete 
volume can be estimated. 

A more refined way of achieving a specified performance in a cost efficient 
manner is to develop "learning curve" type relationships between the two. 
Consider the example in Figure 5-4.  A hypothetical precast concrete tilt-up 
manufacturing facility is to be constructed in a moderately high seismic zone. 
The lowest cost for the building is that which meets the minimum requirements 
of the building code. At this design level, the building will be expected to 
suffer 
some loss in the "worst case" earthquake, however that is defined. Additional 
investments in improved performance might be considered by the design team 
and owner. If the cost for each investment is added cumulatively as each is 
included in the construction budget then the expected worst case loss should 
decrease. As this example shows, investments in postearthquake response 
and nonstructural bracing result in a relatively large benefit in terms of reduced 
losses. Adding interior shear walls results in a moderate benefit. Increasing 
diaphragm strength and changing the entire structural system to unbonded 
braces produce a relatively low benefit. 

This example can be taken further by computing the benefit-cost ratio (BCR) for 
each performance strategy. Suppose the likelihood of the worst case event 
occurring over a 50-year life of the building is 25%, 
which corresponds to a 0.58% annual probability of occurrence2, and that the 
code minimum cost is equal to the replacement cost. Assuming a 5% discount 
rate (rate of return), the resulting benefits and costs are as summarized in 
Table 5-5. 


The example suggests that, in this case, the incorporation of a post-earthquake 
recovery program with a BCR of 2.1 is clearly a good investment. Improving 
nonstructural bracing in addition results in a BCR of 
0.85 suggesting that it is possibly a good investment. The other performance 
strategies appear not to be economically beneficial. 

A careful study of possible design strategies may lead to several cost-per-
formance curves, such as Figure 5-4, incorporating different combinations of 
performance strategies.  These will then allow the owner and the design team 
to select the one that achieves the greatest expected return on the investment. 






5.7 CASE STUDIES OF COST AND PERFORMANCE CONSIDERATIONS 

The following five case studies illustrate how different owners have addressed 
cost and performance considerations in seismic risk management decisions. 

Case Study 1: Computer Graphics Equipment Maker in Salt Lake City, Utah 


Salt Lake City, Utah is the headquarters of a small computer graphics 
equipment maker, as shown in Figure 5-5. The company's main prod
ucts are high-end simulation systems that sell for nearly $10 million 
each. Its new corporate office was to include a large assembly floor in which 
eight to ten of these devices would be assembled at one time, as 
well as a floor of office space above. All of the company's manufactur
ing would be housed within the building. The loss of a single simula
tion device as a result of an earthquake would have caused a 
catastrophic loss for the company, resulting in possible bankruptcy. 
The local structural engineer of record was skilled in performance-
based design and well known in Salt Lake City because of his efforts to 
expand awareness of seismic issues. The engineer was able to develop a 
relationship with the owner directly, although he was part of a design 
team headed by an architect. This "access" to the owner was crucial in 
providing an opportunity for the engineer to explain concepts of per-
formance-based seismic design. He and the owner discussed critical 
structural issues that could affect building performance and impact 
repair costs and business restoration. 

The code in force at the time of construction would likely have protected the 
building against most earthquakes. The seismicity in the Salt Lake City region 
during a typical 30-50 year building life is relatively low. However, considering 
the consequence of damage and lost functionality, even the relatively low 
vulnerability still resulted in an intolerably high risk to the owner. 
Because of the extremely high value of contents and cost of lost opera
tions, a performance objective was established to limit structural and 
nonstructural damage in a rare event to a level that would protect the 
contents and allow operations to continue unimpeded. 

To achieve this performance objective, the building was base isolated. The 
project team justified the additional cost associated with a base isolated 
building over a conventional structure by noting that the cost of the isolated 
structure was still less than the value of a single simulator. The vulnerability 
of 
the enhanced building was substantially lower than would be for a similar 
conventional structure. Much of the equipment, including the simulator devices, 
was braced to prevent tipping or sliding. The overall reduction in risk achieved 
was dramatic and met the owner's risk threshold. To reduce the risk any 
further, the building would likely have to have been re-sited to a region of lower 
seismicity. 


Case Study 2: Salt Lake City, Salt Lake City K-12 School District 

The Salt Lake City School District consists of 30-40 sites and contains 
buildings more than 70 years old, as shown in Figure 5-6. The District 
embarked upon a program of seismically upgrading its buildings to ensure that 
they would be safe and usable following a major seismic event. The District 
made the determination that it wanted to achieve a 70-year additional life for its 
structures. 

Its study of the existing school facilities found that when nonstructural 
rehabilitation costs (e.g., heating, electrical, roofing, and deferred 
maintenance) 
were added to the structural costs necessary to achieve the high performance 
objective, many of the rehabilitations would cost more than the replacement 
cost of the building. In these cases the decision was made to replace the 
facilities with new designs such as that shown in Figure 5-7. 

Recognizing that building codes can change dramatically even over the course 
of ten to twenty years, the District asked its engineering consultant to evaluate 
the performance needs with its long lifetime in mind. The engineer crafted 
simple yet effective graphics similar to the plot shown in Figure 5-8 to help the 
District determine its risk tolerance. A site hazard curve (see discussion in 
Section 3.2) was developed (see Figure 5-8) to show the expected ground 
accelerations plotted against their probability of exceedence in 50 years. Salt 
Lake City is in Uniform Building Code (UBC) Seismic Zone 3, and the vertical 
line at 10% show the design ground motion specified by the UBC. Over a 70-
year period, the probability of exceedence of this level of ground shaking 
increases from 10% to 14%. Another vertical line is drawn at 2% probability of 
exceedence in 50 years, representing perhaps the maximum credible event in 
the area. Over a period of 70 years, the probability of exceedence of this level 
of 
ground shaking increases from 2% to approximately 3%. Most notable is the 
dramatically higher ground motions that would be expected in the 2% 
probability of exceedence in 50-year event. This analysis showed that 
designing only for ground motions having a 10% probability of exceedence in 
50 years meant there was still a risk of much higher ground motions that could 
seriously damage the facilities. The District wanted to achieve a higher level of 
confidence than 14% over the 70-year lifetime that damage would be kept to a 
minimum. The design forces for the 2% probability of exceedence in 50-year 
event compared well to the UBC Seismic Zone 4 design forces. Therefore, the 
District decided to design all its new facilities to Zone 4 requirements for 
forces 
and detailing, pending a cost analysis of the upgraded performance. 

The consulting engineer estimated that to enhance a new facility's design from 
Zone 3 to Zone 4 compliance would add a cost on average of 1/4 to 1% of the 
construction budget. The District quickly realized that amortized over the length 
of its construction financing and certainly over the length of the 70-year 
assumed lifetime, this additional cost was negligible and therefore adopted the 
enhanced design strategy. 

Key factors in the owner's decision to use an enhanced performance objective 
were the expected longevity of the facilities and the number of buildings in the 
portfolio. The importance to the community of the school district, the large 
capital investment that was being made over the entire inventory, and the not 
inconsiderable likelihood of a damaging event occurring over the lives of the 
buildings were also important considerations in the District's decision. 


 
Case Study 3:  Prosthesis Manufacturing Company in Memphis, Tennessee 

A prosthesis manufacturing company in Memphis, Tennessee was nearing 
completion of a 100,000 square foot manufacturing plant in early 2002. The 
products manufactured within the building generate revenues of nearly 
$500,000 per day. The building operations are insured against down time by a 
large international insurance company. 

The building was built to the structural and nonstructural requirements
of the 1997 Southern Building Code (SBCCI, 1997). The insurer offered
to reduce the building's insurance premiums significantly if the nonstructural 
bracing was brought into conformance with the more severe requirements in 
the 2000 International Building Code (ICC, 2000). The International Building 
Code (IBC) requires that nonstructural bracing be designed to consider site 
conditions including soil and proximity to faults, and the location of the 
equipment within the building. 

A New York based manufacturer and supplier of mechanical equipment 
bracing products was hired to assess the additional cost of bracing the 
equipment to the higher standard. Typically, the IBC design required only larger 
elements (e.g., anchor bolts, clevises, rods) and not a substantial change to 
the design configuration. 

The manufacturer performed a detailed comparison of the two codes and 
prepared a side-by-side comparison of the cost premium for the IBC design. 
An excerpt from the comparison is shown in Table 5-6. 
The results of the study showed that the additional cost of upgrading the 
seismic bracing was negligible as a percentage of the overall non-structural 
costs. The company decided, based on the benefit of reduced insurance 
premiums, to implement the higher standard. 

This example suggests that improving the seismic nonstructural bracing in 
new buildings located in moderate seismic zones can be very cost efficient in 
terms of reducing losses. It may also result in the direct benefit of reduced 
annual insurance costs. 



Case Study 4: Stanley Hall, University of California Berkeley 

The University of California (UC) at Berkeley is one of the nation's premier 
research institutions. In 2003 the university broke ground for a state-of-the-art 
bio-engineering laboratory building as shown in Figure 5-9. The estimated cost 
of the project is nearly $200 million. The building will contain high-end 
laboratory facilities and house researchers working annually on nearly $40 
million in grants. UC Berkeley sits astride the active Hayward Fault. In the next 
thirty years, the USGS predicts there is nearly a 30% likelihood of a magnitude 
7 or greater earthquake occurring on the fault (Working Group on California 
Earthquake Probabilities, 2003). 

The University considered the protection of its massive investment in this 
facility to be extremely important. It asked the engineer of record to consider a 
higher performance objective than would have been required by the building 
code in force at the time. The goal was that the facility should remain 
occupiable after a design level event, and repair time to restore full operability 
should be measured in weeks not months. The engineer employed a state-of-
the-art buckling restrained (unbonded brace) braced frame system to ensure 
that damage would be kept to a minimum even in a large event that might 
rupture the entire length of the Hayward Fault. 

In order to obtain financing for the project, the University had to justify the 
added 
expense of the enhanced structural scheme. The school hired a second 
engineering firm expert in risk analysis, to help them provide the necessary 
rationale. The firm developed a "baseline" structural scheme that met only the 
minimum requirements of the building code. This system employed 
conventional concentric braced frames. The difference in cost between the two 
schemes was approximately $1.2 million, or roughly 1/2% of the building cost. 
They then used nonlinear performance-based engineering and risk 
assessment tools to calculate the expected losses due to earthquakes over 
the life of the building. The analysis showed that losses were substantially 
reduced using the enhanced scheme. The overall return on the $1.2 million 
investment, considering reduction of capital, contents and business 
interruption losses was approximately 11%. Figure 5-10 shows that the 
reduction in business interruption provided the majority of the projected 
benefits. Using a 5% discount rate as a benchmark, the benefit-cost ratio 
(BCR) for the enhancements was over 2 considering a fifty year life. At that dis-
count rate, the BCR reached one at a building life of about 15 years as shown 
in Figure 5-11. 

This example suggests that performance-based design can be a very cost 
effective risk management strategy for buildings that generate substantial 
revenue and for which the owner has a long-term interest. 







5.8 QUALITY CONTROL DURING THE CONSTRUCTION PROCESS 

Quality control is an important aspect of assuring satisfactory seismic 
performance: the building must be constructed as designed and specified.  

Building owners often interpret construction quality primarily in relation to 
interior and exterior finishes and materials because these are important for 
"marketing' in the private sector.  It is generally assumed that design and 
construction to meet the applicable building codes will assure a durable and safe 
structure. Since structural elements are usually 
invisible-concealed behind a suspended ceiling, gypsum board or exterior 
cladding-they have little bearing on the perception of building quality.  The 
exterior and interior appearance of the building will typically adhere to a 
company or institutional philosophy; this may be very functional for an industrial 
facility owner, but market trends or institutional objectives may influence 
others. The appearance of all facilities may also be influenced by local community 
design requirements. Decisions about image and quality have a major impact 
on construction cost, both initial and lifetime.  See Section 12.5 for additional 
guidance on assuring design and construction quality. 






5.9 RECOMMENDATIONS FOR IMPROVING SEISMIC PERFORMANCE 

In addition to the specific seismic design issues relating to siting, structural 
systems, and nonstructural systems, there are some general measures that 
can be employed to help manage seismic risk by reducing either the 
vulnerability of the facility to earthquake damage, or the consequences of the 
damage should it occur. These measures include the following. 

Consideration should be given to performance-based design to a level 
beyond Life Safety (typically the level of performance provided by provisions of 
the current seismic design codes) to a level of Immediate Occupancy, as 
discussed in Section 4.3. Institutional, public and corporate owners usually 
have long-term ownership of their facilities and a desire for continued operation 
in the post-event period. 

The design professionals in charge of the structural and nonstructural 
component installation should specify quality assurance requirements; the 
contractor should be required to exercise a high degree of quality control; and 
independent inspection should be used to ensure conformance to 
requirements. 

The design engineer should advise facility owners and manager on 
technical  aspects of obtaining insurance to cover potential losses including 
service interruption.  It may be possible to negotiate reduced premiums with 
the insurance carrier on the basis of any seismic mitigation measures 
provided beyond the code-minimum requirements. 

Retainer agreements should be established with engineers and 
architects to provide building inspection services immediately following an 
earthquake (see Section 2.6 for additional information). 

Personal protection and evacuation plans should be developed for all 
staff and students. Regular drills and educational sessions should be 
conducted to ensure proper execution (see Section 2.6 for additional 
information).