Tsunami Forces on Structures
Tsunami Forces on Structures
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Chapter 11
11.1. Introduction
                                                                                    Tsunami waves represent extreme, often catastrophic events, which significantly and
                                                                                    adversely impact coastal areas. In spite of the lower frequency of occurrence com-
                                                                                    paring to storms and storm-induced surges, tsunami-induced coastal flooding often
                                                                                    leads to massive casualties and tremendous economic losses.1–3 Hence, tsunamis are
                                                                                    rare events, high-impact natural disasters.
                                                                                        The devastating effects of the 26 December 2004 Tsunami on many coun-
                                                                                    tries bordering the Indian Ocean raised public concern and revealed existing defi-
                                                                                    ciencies within the current warning and defense systems against tsunamis. One of
                                                                                    the important elements that needs significant improvement is the estimation of
                                                                                    forces generated by tsunami-induced bores, as well as water-borne debris. Before
                                                                                    the 2004 Indian Ocean Tsunami, the design of structures against tsunami-induced
                                                                                    forces was considered of minor importance when compared to the attention given
                                                                                    to tsunami warning systems. This was due to the assumption that tsunamis are
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                                                                                                          (a)                                           (b)
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(c) (d)
                                                                                    Fig. 11.1. Tsunami damage in Thailand and Indonesia (December 2004 Indian Ocean Tsunami):
                                                                                    (a) severe structural damage, Khao Lak, Thailand; (b) column failure of a reinforced con-
                                                                                    crete frame, Phuket, Thailand; (c) column failure due to debris impact, Banda Aceh, Indonesia;
                                                                                    (d) punching failure of infill walls, Banda Aceh, Indonesia.4
                                                                                    rare events, with significantly high return periods (sometimes more than 500 years).
                                                                                    Reconnaissance missions of the December 2004 Indian Ocean Tsunami disaster
                                                                                    revealed that tsunami-induced forces can lead to severe damage or collapse of struc-
                                                                                    tures as shown in Fig. 11.1.3–11 Therefore, these forces should be properly accounted
                                                                                    for in the design of infrastructure built within a certain distance from the shoreline
                                                                                    in tsunami-prone areas.
                                                                                        The design of coastal structures such as breakwaters, jetties, and groins against
                                                                                    waves is typically based on considering the effect of breaking waves and their asso-
                                                                                    ciated forces, and is well established. Unlike coastal structures, the evaluation of
                                                                                    tsunami-induced hydrodynamic forces on structures used for habitation and/or eco-
                                                                                    nomic activity, received little attention by researchers and engineers.
                                                                                        Results of field surveys conducted in the aftermath of the December 2004 Indian
                                                                                    Ocean Tsunami in Indonesia and Thailand showed that poorly detailed concrete
                                                                                    structures experienced severe damage.3,4 This highlighted the fact that the current
                                                                                    structural design codes do not account for tsunami-induced forces and the impact
                                                                                    of associated debris. Reinforced concrete structures have been observed to with-
                                                                                    stand tsunamis with acceptable low levels of damage.12 However, as shown in
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Damage
Partial Damage
Withstand
                                                                                                        0   1       2        3      4      5        6   7                     20
                                                                                                                                                               Lack of data
                                                                                                            Inundation Depth (m)
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                                                                                    Fig. 11.2. Relation between the inundation depth and degree of damage to reinforced concrete
                                                                                    buildings.13
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                                                                                    Fig. 11.2, inundation depths of more than 5 m can induce partial damage to concrete
                                                                                    structures.
                                                                                        Currently, there are no clearly established procedures to address the aforemen-
                                                                                    tioned forces. Moreover, significant disagreement on existing empirical formulae fos-
                                                                                    tered new research interest in an effort to properly address the inclusion of both
                                                                                    tsunami-induced forces and the impact of debris into design codes. Aspects related
                                                                                    to these forces are discussed in this chapter. Some of the shortcomings and incon-
                                                                                    sistencies of existing codes are also highlighted.
                                                                                                          (a)                                                (b)
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(c) (d)
                                                                                    Fig. 11.3. Tsunami wave in Khao Lak, Thailand (December 2004 Indian Ocean Tsunami):
                                                                                    (a) water recedes; (b) waves approach the shoreline; (c) tsunami waves break close to the shoreline;
                                                                                    (d) tsunami waves inundate the shoreline.14
                                                                                    Snodgrass et al.23 noticed that broken waves induced larger hydrodynamic hori-
                                                                                    zontal forces on a test pile compared to waves breaking at the pile location. As
                                                                                    previously mentioned, broken tsunami waves inundate shoreline in the form of a
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                                                                                    hydraulic bore, which is a fast moving body of water with an abrupt front. However,
                                                                                    mechanisms of impingement of broken tsunami waves on structures located inland
                                                                                    are not yet well understood.
                                                                                        Pioneering analytical and experimental attempts to quantify forces due to bores
                                                                                    date back to Stoker,24 Cumberbatch,25 Fukui,26 Cross,27 and Dames and Moore.28
                                                                                    Comprehensive experimental investigation of the interaction of bores and dry-
                                                                                    bed surges with a vertical wall was performed by Ramsden and Raichlen29 and
                                                                                    Ramsden.30,31 In these experiments, three flow conditions were analyzed: (1) tur-
                                                                                    bulent bores (initial still water downstream of the gate); (2) dry-bed surges (no
                                                                                    initial water depth downstream of the gate); and (3) solitary waves. Forces and over-
                                                                                    turning moments due to bores and dry-bed surges were recorded and calculated,
                                                                                    respectively. The results of Ramsden’s studies are not applicable to the estimation
                                                                                    of impulsive forces.31 It was observed that the pressure distribution during impact
                                                                                    is essentially nonhydrostatic. The experiment also demonstrated that the transition
                                                                                    from undular to turbulent bores led to a discontinuous increase in water-surface
                                                                                    slope, followed by an increase in measured runup, pressure head, and exerted forces
                                                                                    and moments. Figure 11.4 shows the difference between a strong turbulent bore and
                                                                                    a dry-bed surge with approximately the same celerity.
                                                                                        It was shown that recorded forces gradually increased to an approximately con-
                                                                                    stant value for both the case of a surge and a bore. No impulsive (shock) force
                                                                                    exceeding the hydrodynamic force was observed. However, an initial impulsive
                                                                                    pressure equal to three times the pressure head, corresponding to the mea-
                                                                                    sured runup, was recorded. Ramsden31 further derived empirical formulae for the
                                                                                    maximum force and moment exerted on a vertical wall due to the bore impact
                                                                                    [Eqs. (11.1) and (11.2)].
                                                                                                                                         
                                                                                                                                           3     2
                                                                                                 F                        H          1 1   H   H
                                                                                                    = 1.325 + 0.347               ++            ,                   (11.1)
                                                                                                 Fl                       h         58.5
                                                                                                                                     7160 h    h
                                                                                                                             2        3
                                                                                                 M                   H     1   H      1   H
                                                                                                    = 1.923 + 0.454     +          +          ,                     (11.2)
                                                                                                 Ml                  h    8.21 h     808 h
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                                                                                    Fig. 11.4. Comparison of: (a) wave profile; (b) runup; (c) pressure head; (d) force due to a strong
                                                                                    turbulent bore and a dry-bed surge.31
                                                                                    where F is the force on the wall; Fl is the force on the wall due to a runup equal to
                                                                                    twice the wave height, assuming hydrostatic pressure; H is the wave height at the
                                                                                    wall; h is still water depth; M is the moment on the wall; and Ml is the moment
                                                                                    corresponding to Fl .
                                                                                       Okada et al.32 conducted a survey of previous studies on tsunami wave forces
                                                                                    and pressures, and identified five empirical formulae for tsunami-induced forces or
                                                                                    pressures. It was found that calculation of tsunami load on structures using these
                                                                                    formulae would result in approximately the same magnitude of load. These formulae
                                                                                    are as follows:
Fig. 11.5. Measured and nondimensional force history for a square column.37
350
                                                                                                                                           250
                                                                                                                               Force (N)
                                                                                                                                           150
                                                                                                                                                                                                                            h0 = 1.00 m
                                                                                                                                                                                                                            h0 = 0.85 m
                                                                                                                                           50
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                                                                                                                                           -50
                                                                                                                                              10           12          14           16                                     18          20            22
                                                                                                                                                                                 Time (s)
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Fig. 11.6. Time history of exerted forces on a circular structure38 ; h0 is the impoundment depth.
                                                                                                                        60                                                                                            60
                                                                                    Height of the structure (cm)
50 50
                                                                                                                        40                                 t=0.000 s                                                  40
                                                                                                                                                                                                                                                     t=0.160 s
                                                                                                                                                           t=0.006 s                                                                                 t=0.170 s
                                                                                                                        30                                 t=0.006 s                                                  30                             t=0.180 s
                                                                                                                                                           t=0.009 s                                                                                 t=0.190 s
                                                                                                                        20                                                                                            20
10 10
                                                                                                                         0                                                                                             0
                                                                                                                   -2           3                  8             13         18                                   -2             3               8          13        18
                                                                                                                                                 P (kPa)                                                                                   P (kPa)
                                                                                    Fig. 11.7. Variation of pressure distribution on the front face — circular structure38 ; t = 0.0 s is
                                                                                    the instant when the bore impacts the structure.
Fm/γ D2L
σf / γL = 2000
                                                                                                                                                1500
                                                                                              120
                                                                                                                                                   1000
                                                                                                                                                    500
                                                                                               80
                                                                                                                                                     200
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                                                                                                                                                     100
                                                                                               40
                                                                                                                                                       20
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                                                                                                0
                                                                                                    0.0                    1.0               2.0              3.0            VA0/(gD)0.5
Fig. 11.8. Impact forces of wood logs for bores and surges.39
                                                                                    where γw is the specific weight of wood, D is the diameter of the log, L is the
                                                                                    length of the log, CM is a coefficient which depends on the flow passing around the
                                                                                    receiving wall (≈ 1.7 for bore or surge, and 1.9 for steady flow), u is the velocity of
                                                                                    the log at impact, and σf is the yield stress of the log. Figure 11.8 shows the design
                                                                                    chart based on Eq. (11.3).
                                                                                        Currently, three basic models are proposed for estimating the forces due to the
                                                                                    impact of debris on structures, which are used by a few design codes. In these
                                                                                    models, the impact force is calculated based on the mass and velocity of debris,
                                                                                    while ignoring the mass and rigidity of the structure. However, other than the mass
                                                                                    and velocity of debris, each model needs an additional parameter. The three models
                                                                                    and their corresponding additional parameters are
                                                                                    a large basin where water was stationary and logs were placed on a movable car-
                                                                                    riage. The effect of parameters such as added mass of the water and the eccentricity
                                                                                    and obliqueness of the collision were also considered. Figure 11.9 shows the effect of
                                                                                    impact orientation on the measured force. It was found that the maximum impact
                                                                                    force, Fi,max , can be calculated using Eq. (11.4).
                                                                                                                                            
                                                                                                                Fi,max = Maxk̂x = u        k̂m1 ,                    (11.4)
                                                                                    where u is the impact velocity of the log, k̂ is the constant effective stiffness between
                                                                                    the log and the structure, and m1 is the mass of the log. Based on experiments,
                                                                                    Haehnel et al.40 found the value of k̂ = 2.4 MN/m to be the representative for the
                                                                                    upper envelope of the collected data.
                                                                                    At present, only four design codes and guidelines specifically account for tsunami-
                                                                                    induced loads as listed below:
                                                                                    • FEMA 55: The code is adopted by the Federal Emergency Management Agency,
                                                                                      the United States, and recommends formulae for tsunami-induced flood and wave
                                                                                      loads.43
                                                                                    • The City and County of Honolulu Building Code (CCH): The code, developed
                                                                                      by the Department of Planning and Permitting of Honolulu, Hawaii, United
                                                                                      States, makes provisions for regulations that apply to districts located in flood
                                                                                      and tsunami-risk areas.44
                                                                                    • Structural Design Method of Buildings for Tsunami Resistance (SMBTR): The
                                                                                      code is proposed by the Building Center of Japan32 and outlines the structural
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                                                                                       There are several other design codes (sometimes country-specific) which contain
                                                                                    prescriptions and design guidelines for flood-induced loads. Examples of widely used
                                                                                    codes are indicated below:
                                                                                       However, none of the above codes address directly the tsunami-induced forces,
                                                                                    which represent the focus of this chapter. The reader is advised to refer to these
                                                                                    codes when seeking guidance for the design of structures subjected to flood-induced
                                                                                    loads other than tsunamis: coastal flooding due to storm surges, flooding of river
                                                                                    banks above bank-full conditions, etc.
                                                                                    (drag) force, (3) buoyant force, (4) surge force, and (5) impact of debris. A brief
                                                                                    description of these forces is further presented.
                                                                                                                                     2
                                                                                                                         1        u2p
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                                                                                                                  FHS   = ρg dS +        .                          (11.5)
                                                                                                                         2        2g
FB = ρgV, (11.6)
                                                                                    below.
                                                                                    Tsunami-bore Velocity. Previous research shows that significant differences in esti-
                                                                                    mating forces exerted on structures by tsunami bores, as well as impact of debris,
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                                                                                    are due to differences in estimating bore velocity. Since the hydrodynamic force is
                                                                                    proportional to the square of the bore velocity, uncertainties in estimating veloc-
                                                                                    ities induce large differences in the magnitude of the resulting hydrodynamic force.
                                                                                    Tsunami-bore velocity and direction can vary significantly during a major tsunami
                                                                                    inundation. Current estimates of the velocity are crude; a conservatively high flow
                                                                                    velocity impacting the structure at a normal angle is usually assumed. Also, the
                                                                                    effects of runup, backwash, and direction of velocity are not addressed in the current
                                                                                    design codes.
                                                                                        Although there is certain consensus in the general form of equation for the
                                                                                    hydrodynamic force, several researchers proposed different empirical coefficients.
                                                                                    The general form of the bore velocity is shown below [Eq. (11.8)]:
                                                                                                                              
                                                                                                                         u = C gds ,                               (11.8)
                                                                                    where u is the bore velocity, ds is the inundation depth, and C is a constant
                                                                                    coefficient.
                                                                                       Various formulations were proposed by FEMA 55 (based on Dames and
                                                                                    Moore28 ), Iizuka and Matsutomi,35 CCH,44 Kirkoz,50 Murty,51 Bryant,52 and
                                                                                    Camfield53 for estimating the velocity of a tsunami bore in terms of inundation
                                                                                    depth (Fig. 11.10). Velocities calculated using CCH and FEMA 55 represent a lower
                                                                                    and upper boundary, respectively.
                                                                                                           16
                                                                                                                        CCH: u=h
                                                                                                                        FEMA 55: u=2(gh)^0.5
                                                                                                                        Iizuka: u=1.1(gh)^0.5
                                                                                                           12           Kirkoz: u=(2gh)^0.5
                                                                                                                        Murty: u=1.83(gh)^0.5
                                                                                                                        Bryant: u=1.67h^(0.7)
                                                                                                 V (m/s)
                                                                                                            4
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                                                                                                            0
                                                                                                                0                         2                       4                    6
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d S (m)
                                                                                                                                                                            building
                                                                                                                                                             qx
                                                                                                                                     3h
                                                                                                 Design inundation depth
                                                                                                                                               z
                                                                                                                                                     h
                                                                                             z
                                                                                                                                                                  3ρgh
Fig. 11.11. Tsunami wave pressure for structural design recommended by SMBTR.32
                                                                                    where qx is the tsunami wave pressure for structural design, z is the height of the
                                                                                    relevant portion from ground level (0 ≤ z ≤ 3h), ρ is the mass per unit volume of
                                                                                    water, and g is the gravitational acceleration.
                                                                                        Integration of the wave pressure formula for walls with heights equal to or greater
                                                                                    than 3h results in the same equation as the surge force formula recommended by
                                                                                    CCH [Eq. (11.9)]. The magnitude of the surge force calculated using Eqs. (11.9)
                                                                                    and (11.10) will generate a value equal to nine times the magnitude of the hydro-
                                                                                    static force for the same flow depth. However, a number of experiments31,37 did not
                                                                                    capture such differences in magnitude. Yeh et al.45 commented on the validity of
                                                                                    Eq. (11.9) and indicated that this equation gives “excessively overestimated values.”
                                                                                    On the other hand, Nakano and Paku46 conducted extensive field surveys in order
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                                                                                    to examine the validity of the proposed tsunami wave pressure formula [Eq. (11.10)].
                                                                                    The coefficient 3.0 in Eq. (11.10) was taken as a variable, α, and was calculated
                                                                                    such that it could represent the boundary between damage and no damage in the
                                                                                    surveyed data. A value of α equal to 3.0 and 2.0 was found for walls and columns,
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                                                                                    respectively. The former is in agreement with the proposed formulae by both CCH
                                                                                    and SMBTR [Eqs. (11.9) and (11.10)].
                                                                                        The tsunami wave force may be composed of drag, inertia, impulse, and
                                                                                    hydraulic gradient components. However, SMBTR does not specify different compo-
                                                                                    nents for the tsunami-induced force, and the proposed formula presumably accounts
                                                                                    for other components.
                                                                                                                              dub   ui
                                                                                                                    Fi = mb       =m ,                             (11.11)
                                                                                                                               dt   ∆t
                                                                                    where Fi is the impact force, mb is the mass of the body impacting the structure,
                                                                                    ub is the velocity of the impacting body (assumed equal to the flow velocity), ui is
                                                                                    approach velocity of the impacting body (assumed equal to the flow velocity), and
                                                                                    ∆t is the impact duration taken equal to the time between the initial contact of the
                                                                                    floating body with the building and the instant of maximum impact force.
                                                                                        The only difference between CCH and FEMA 55 resides in the recommended
                                                                                    values for the impact duration which has a noticeable effect on the magnitude of
                                                                                    the force. For example, CCH recommends the use of impact duration of 0.1 s for
                                                                                    concrete structures, while FEMA 55 provides different values for walls and piles for
                                                                                    various construction types as shown in Table 11.1.
                                                                                        According to FEMA 55, the impact force (a single concentrated load) acts hor-
                                                                                    izontally at the flow surface or at any point below it. Its magnitude is equal to
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                                                                                    the force generated by 455 kg (1000-pound) of debris traveling with the bore and
                                                                                    acting on a 0.092 m2 (1 ft2 ) surface of the structural element. The impact force is
                                                                                    to be applied to the structural element at its most critical location, as determined
                                                                                    by the structural designer. It is assumed that the velocity of the floating body goes
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                                                                                    from ub to zero over some small finite time interval (∆t). Finding the most critical
                                                                                    location of impact is a trial and error procedure that depends, to a large extent, on
                                                                                    the experience and intuition of the engineer.
                                                                                     (i) FEMA 55 does not provide loading combinations specifically for calculation
                                                                                         of tsunami force. However, flood load combinations can be used as guidance.
                                                                                         Flood load combinations for piles or open foundations, as well as solid walls
                                                                                         (foundation) in flood hazard zones and coastal high hazard zones are presented
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                                                                                         as follows:
                                                                                         Pile or open foundation:
                                                                                         Fbrkp (on all piles) + Fi (on one corner or critical pile only), or
                                                                                         Fbrkp (on front row of piles only) + Fdyn (on all piles but front row) +
                                                                                         Fi (on one corner or critical pile only).
                                                                                         Solid (wall) foundation:
                                                                                         Fbrkw (on walls facing shoreline, including hydrostatic component) +
                                                                                         Fdyn (assumes one corner is destroyed by debris),
                                                                                         where Fbrkp , Fi , Fdyn , and Fbrkw refer to breaking force on piles, impact force,
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                                                                                         hydrodynamic force, and breaking force on walls, respectively. The reader can
                                                                                         refer to FEMA 5543 for more details.
                                                                                    (ii) Yeh et al.45 modified flood load combinations provided by FEMA 55 and
                                                                                         adapted them for tsunami forces as follows:
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(a) (b)
                                                                                                    Fd                               Fd
                                                                                                    Fs                               Fs                              Fs
                                                                                                                      W                               W- V
                                                                                    Fig. 11.12. Loading combinations: (a) point of impact/not submerged; and (b) post-submergence/
                                                                                    submerged.54
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(a)
Fi
h FS
                                                                                                   (b)
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                                                                                                                              Fi
                                                                                             dS                               Fd
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                                                                                                                              FHS                               FHS
                                                                                          Fig. 11.13.    Proposed loading conditions: (a) point of impact; and (b) post-impact.42
                                                                                    (iv) Nouri et al.42 proposed two new load combinations based on the two condi-
                                                                                         tions considered by Dias et al.,54 as shown in Fig. 11.13. The proposed load
                                                                                         combinations by Nouri et al.42 are adapted to follow a consistent format as the
                                                                                         above combinations:
                                                                                          Columns:
                                                                                          Fs (on front row of piles only) + Fi (on one corner or critical column in the
                                                                                          front row only), or
                                                                                          Fd (on all piles) + Fi (on one corner or critical column only),
                                                                                          where Fs is the surge force on walls.
                                                                                          Solid (wall) foundation:
                                                                                          Fs (on walls facing shoreline) + Fi (on walls facing shoreline), or
                                                                                          Fd (on walls facing shoreline) + Fi (on one critical wall facing shoreline) +
                                                                                          Fb (on submerged section of the structure).
                                                                                    Building codes provide guidance for the design of lateral force resisting systems
                                                                                    subjected to wind and seismic excitations. Tsunami-induced loading is normally
                                                                                    not considered. The objective of this example is to demonstrate the levels of
                                                                                    lateral loading associated with tsunamis for a prototype reinforced concrete building
                                                                                    located in a tsunami-prone area. Specifically, the loads generated by a tsunami
                                                                                    bore are addressed. Other researchers have provided comparisons between tsunami
                                                                                    loading and other lateral loads (Okada et al.,32 Pacheco and Robertson,55 Nouri
                                                                                    et al.,42 and Palermo et al.56 ).
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                                                                                                                                                                               6.0
                                                                                                              B
                                                                                                    Tsunami
                                                                                                                                                                               6.0
                                                                                                              C
                                                                                                                                                                               6.0
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                                                                                                                    1          2         3           4         5         6
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Fig. 11.14. Plan view of structural layout of reinforced concrete moment-resisting frame.56
                                                                                    the entire surface of the building. In this situation, the drag coefficients are taken
                                                                                    as 1.5 and 1.25 for CCH and FEMA 55, respectively.
example.
                                                                                    In this example, the surge force is applied over the full length of the building in the
                                                                                    direction of the tsunami for nonbreakaway walls. For the case of 100% breakaway
                                                                                    walls, it is assumed that the surge force will develop on the four exterior columns
                                                                                    which face the hydraulic bore. Note that the surge force is not applicable for FEMA
                                                                                    55 and that SMBTR assumes a different surge force per unit width for columns and
                                                                                    walls, as mentioned in Sec. 11.3.1.4.
Drag Force:
                                                                                                                                        ρCD Au2
                                                                                                                              FD =
                                                                                                                                           2
                                                                                                                                	
                                                                                                                                     m           m
                                                                                                          u = C gds = 2           9.81 2 (5 m) = 14 ;                      FEMA 55
                                                                                                                                      s            s
                                                                                                                                             m
                                                                                                                              u = ds = 5       ;                              CCH
                                                                                                                                             s
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                             2
                                                                                            1030 kg/m3 (2)(56 m2 ) (14m/s)
                                                                                    FD =                                    = 11,317 × 103 N = 11,317 kN; FEMA 55
                                                                                                         2
                                                                                                  
                             2
                                                                                                   1030 kg/m3 (2)(56 m2 ) (5 m/s)
                                                                                           FD   =                                  = 1442 × 103 N = 1442 kN.                  CCH
                                                                                                                2
                                                                                    Debris Impact Force:
                                                                                                                                  
                                                                                                       ui                 14m/s
                                                                                                Fi = m    = 455 kg                      = 21.2 × 103 N = 21 kN;            FEMA 55
                                                                                                       ∆t                  0.3 s
                                                                                                                                   
                                                                                                                           5 m/s
                                                                                                        Fi = 455 kg                     = 22.8 × 103 N = 23 kN.               CCH
                                                                                                                            0.1 s
                                                                                                                       m                     kg
                                                                                                            g = 9.81      ;    ρ = 1030         ;   ds = 5 m
                                                                                                                       s2                    m3
                                                                                    Surge Force:
                                                                                                                                  
                                                                                                                               N
                                                                                                       FS =       1.14 × 106           (18 m + 0.45 m)
                                                                                                                               m
                                                                                    Drag Force:
                                                                                                                                    ρCD Au2
                                                                                                                            FD =
                                                                                                                                       2
                                                                                                                          CD = 1.25 Walls                               FEMA 55
                                                                                                                          CD = 1.5 Walls                                   CCH
                                                                                                               A = (5 m)(18 m + 0.45 m) = 92 m2 ;
                                                                                                               
          
                                                                                                                1030 kg/m3 (1.25)(92 m2 ) (14 m/s)2
                                                                                                          FD =
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                                                                                                                               2
                                                                                                              = 11,652 × 103 N = 11,652 kN;                             FEMA 55
                                                                                                 
               
            2
                                                                                                  1030 kg/m3 (1.5) 92 m2 (5 m/s)
           by KAINAN UNIVERSITY on 02/15/17. For personal use only.
                                                                                    11.4.6. Results
                                                                                    Tables 11.2 through 11.7 provide the results for the calculation of the individual
                                                                                    force components for the structure considered using CCH, FEMA 55, and SMBTR,
                                                                                    respectively.
                                                                                        Given the force components, a loading combination must be specified in order
                                                                                    to evaluate the maximum tsunami load that would be used for either design or
                                                                                    analysis purposes. Yeh et al.45 suggested loading combinations that are applicable
                                                                                    for tsunami loading. CCH does not specifically provide guidance to evaluate the
                                                                                    maximum tsunami load. Nouri et al.42 proposed a two-part loading combination:
                                                                                    Initial impact and Post-impact flow. For this example, these loading combinations
                                                                                    are similar to those of Nouri et al.42 Table 11.8 provides the results of the tsunami
                                                                                                 CCH            1               1          82      12         5
                                                                                                                2               2         327      92         9
                                                                                                                3               3         737     311        14
                                                                                                                4               4        1310     738        18
                                                                                                                5               5        2046    1442        23
             July 31, 2009 8:18                                                                                   9.75in x 6.5in                                b684-ch11          FA
                                                                                               CCH            1                1          839          14           5
                                                                                                              2                2         3356         114           9
                                                                                                              3                3         7550         385          14
                                                                                                              4                4       13,423         912          18
                                                                                                              5                5       20,973        1782          23
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                                                                                                FEMA 55             1                 6              453         10
                                                                                                                    2                 9             1811         13
                                                                                                                    3                11             4074         16
                                                                                                                    4                13             7243         19
                                                                                                                    5                14           11,317         21
                                                                                                FEMA 55             1                 6              466         10
                                                                                                                    2                 9             1864         13
                                                                                                                    3                11             4195         16
                                                                                                                    4                13             7457         19
                                                                                                                    5                14           11,652         21
                                                                                    load calculation for CCH, FEMA 55 and SMBTR for an inundation depth of 5 m
                                                                                    based on loading combinations of Nouri et al.42
                                                                                        For the prototype moment-resisting frame structure with the short side per-
                                                                                    pendicular to the advancing bore, it is apparent that nonbreakaway walls or rigid
                                                                                    exterior nonstructural components can lead to large design base shears. CCH and
                                                                                    SMBTR estimate significantly larger base shears relative to FEMA 55 due to the
                                                                                    omission of a surge component in FEMA 55. It is evident that the width of exposed
                                                                                    surfaces affects the magnitude of total forces exerted on a structure. Therefore, it
                                                                                    would be prudent to orient buildings such that the short side is placed parallel to the
                                                                                    shoreline. Furthermore, using breakaway or flexible walls at the lower level would
                                                                                    reduce the lateral force that is transmitted to the lateral force resisting system. Note
                                                                                    that although the debris impact force is a negligible component in the base shear,
             July 31, 2009 8:18                                                                                  9.75in x 6.5in                          b684-ch11        FA
                                                                                                       SMBTR                  1                    36
                                                                                                                              2                   146
                                                                                                                              3                   327
                                                                                                                              4                   582
                                                                                                                              5                   909
                                                                                                       SMBTR                  1                    839
           by KAINAN UNIVERSITY on 02/15/17. For personal use only.
                                                                                                                              2                   3356
                                                                                                                              3                   7550
                                                                                                                              4                 13,423
                                                                                                                              5                 20,973
                                                                                          Table 11.8. Tsunami-induced load based on CCH, FEMA 55, and SMBTR for
                                                                                          5 m inundation depth.
Acknowledgment
References
                                                                                     1. D. C. Cox and J. F. Mink, Bull. Seism. Soc. Am. 53, 1191–1209 (1963).
                                                                                     2. H. Yeh, Natural Hazards 4, 209–220 (1991).
             July 31, 2009 8:18                                                                                    9.75in x 6.5in                      b684-ch11                 FA
                                                                                    31. J. D. Ramsden, J. Waterways, Port, Coastal and Ocean Eng. 122(3), 134–141 (1996).
                                                                                    32. T. Okada, T. Sugano, T. Ishikawa, S. Takai and T. Tateno, The Building Centre of
                                                                                        Japan (2005).
                                                                                    33. R. Asakura, K. Iwase and T. Iketani, Proc. Coastal Eng. JSCE 47, 911–915 (2000).
                                                                                    34. M. Ikeno, N. Mori and H. Tanaka, Proc. Coastal Eng. JSCE 48, 846–850 (2001).
                                                                                    35. H. Iizuka and H. Matsutomi, Proc. Conf. Coastal Eng., JSCE 47 (2000) (in Japanese).
                                                                                    36. M. Omori, N. Fujii and O. Kyotani, Proc. Coastal Eng. JSCE 47, 376–380 (2000).
                                                                                    37. H. Arnason, PhD thesis, University of Washington, Seattle (2005), p. 172.
                                                                                    38. Y. Nouri, I. Nistor, D. Palermo and A. Cornett, Coastal Structures 2007, Venice, Italy
                                                                                        (2007).
                                                                                    39. H. Matsutomi, J. Hyd. Coastal Environ. Eng. JSCE, No. 621/II-47, 111–127 (1999)
                                                                                        (in Japanese, with English abs.).
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