16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017
Paper N° 1948 (Abstract ID)
Registration Code: S-E1464705294“ANTI-CATASTROPHE” CONCEPT IN JAPANESE SEISMIC DESIGN CODES
A. Nozu(1), Y. Murono(2), Y. Takahashi(3), M. Akiyama(4), S. Kataoka(5), R. Honda(6)(1)

Director of Earthquake Disaster Prevention Engineering Division, Port and Airport Research Institute, nozu@pari.go.jp
Director, Center for Railway Earthquake Engineering Research, Railway Technical Research Institute, murono@rtri.or.jp(3)
Associate Professor, Kyoto University, takahashi.yoshikazu.4v@kyoto-u.ac.jp(4)
Professor, Waseda University, akiyama617@waseda.jp(5)
Head of Earthquake Disaster Management Division, National Institute for Land and Infrastructure Management, kataokas92rc@nilim.go.jp(6)Professor, The University of Tokyo, rhonda@k.u-tokyo.ac.jp(2)

Abstract
In light of the serious tsunami disaster during the 2011 Tohoku earthquake and the subsequent severe accident at the
Fukushima-Daiichi Nuclear Power Plant, the preparedness of infrastructures such as railway structures, highway structuresand port structures to unexpected events became a big issue among civil engineers in Japan. In the conventional seismic
design of these structures, basically two kinds of design ground motions, namely, the level 1 and 2 design ground motions
are considered and the structures are designed so that they fulfill respective performance requirements through verification.
In particular, significantly intense ground motions from shallow crustal and subduction earthquakes have been considered as
the level 2 design ground motions. However, it is still necessary to consider the performance of structures to unexpected
events and its consequences, mainly because of our insufficient knowledge of natural phenomena and of the performance ofstructures itself. Therefore, the authors proposed a new design concept called the “anti-catastrophe design concept”. In thisconcept, a structure is said to be “anti-catastrophe” when the structure or the structure-environment system does not exhibit
catastrophic situation even in an unexpected event. In order to contribute to the establishment of the “anti-catastrophe”
design concept of structures, the design standards for railway structures, highway structures, and port structures in Japan are
reviewed. In all of these codes, the necessity to consider the performance of structures to unexpected events and its
consequences are recognized. For the railway structures, devices have been developed for the anti-catastrophe design
including the “dead weight compensation mechanism”. For the highway structures, “unseating prevention devices” havewidely been used in the design of bridges. For the port structures, efforts are being made to improve the performance of
breakwaters after they are affected by extreme tsunamis. One of the most important ingredients of the “anti-catastrophe
design” is to understand the performance of a structure or a structure-environment system under extreme external forces tounderstand its consequences. In this respect, the “anti-catastrophe design” is oriented in the same direction as the “riskinformed design” proposed in the revised version of ISO2394. However, as mentioned above, the Japanese engineers seemto put more emphasis on the development of measures or devices to cope with this issue. It should be noted that ourknowledge is quite limited in terms of the performance of a structure or of a structure-environment system subject toextreme events. Obviously more effort is needed to understand the performance of structures to extreme events. To this end,
every kind of available tools should be used. For example, model tests and numerical simulations could be useful. On theother hand, it is not reasonable to think that the performance of such devices or measures should always be evaluatedquantitatively. Sometimes, other human abilities such as intuition and insight could be useful in developing measures anddevices. As an example, although we do not know the detailed stress history of unseating prevention devices during anearthquake, they have widely been used in the design of highway bridges in Japan and some of those devices performed
well in the past earthquakes. After all, we should mobilize all kinds of human ability, ranging from intuition or insight tomore sophisticated engineering skills, to cope with the issue of the preparedness of structures to unexpected events.
Keywords: Anti-catastrophe design; design code; unexpected event; extreme event; consequence16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

1. Introduction
In light of the serious tsunami disaster during the 2011 Tohoku earthquake and the subsequent severe accident at
the Fukushima-Daiichi Nuclear Power Plant, civil engineers in Japan have been discussing the preparedness of
infrastructures such as railway structures, highway structures and port structures to unexpected events. The
authors formed a working group to discuss this issue within the framework of the Earthquake Engineering
Committee, the Japan Society of Civil Engineers.
In the conventional seismic design of these structures, basically two kinds of design ground motions,
namely, the level 1 and 2 design ground motions are considered and the structures are designed so that they
fulfill respective performance requirements through verification. In particular, the level 2 design ground motion
is determined by taking into account severe ground motions from shallow crustal and subduction earthquakes
and the structures are designed so that the ultimate limit state is not exceeded. In this process, less attention has
been paid to the performance of structures subject to a strong ground motion exceeding the level 2 design groundmotion and to its consequences.
In light of the lessons learnt from the 2011 Tohoku earthquake, however, the working group recognized
the necessity to consider the performance of structures under unexpected events and its consequences mainly
because of the following two reasons.
1. The level 2 design ground motions may be exceeded during the design working life of a structure irrespectiveof the method that is used to determine the level 2 design ground motion because of our insufficientknowledge of natural phenomena.
2. Structures may exhibit unexpected performance leading to damage even when the level 2 design groundmotion is not exceeded.
Therefore, the working group proposed a new design concept called the “anti-catastrophe design concept” [1]. In
this concept, a structure is said to be “anti-catastrophe” when the structure or the structure-environment systemdoes not exhibit catastrophic situation even in an unexpected event. The working group has started developing aframework for the design of structures based on this concept [1].
In the “anti-catastrophe design”, a scenario involving a collapse of a structure is considered, irrespectiveof the strength of the structure. Then, the performance not only of the structure itself but also of the structureenvironment system is considered. Based on the expected consequences, possible measures are taken not only inthe process of structural design but also during planning. For example, when we discuss the ability of abreakwater to delay the inundation of tsunamis, the tsunami-affected region including the breakwater isconsidered as a system. When we discuss the redundancy of a transportation system, the road network is
considered as a system. Although simulations of tsunami inundation have been conducted in the practice ofregional disaster planning in Japan, what’s new about the “anti-catastrophe design” is that it is conducted in theprocess of designing structures, probably under the leadership of engineers, thereby making it possible to takeappropriate measures in the design and planning.
The relationship between the conventional seismic design and the anti-catastrophe design can be shown as
in Fig. 1. As shown in Fig. 1, the conventional seismic design is based on the process of verification of theperformance of structures for design ground motions (blue). There are events, however, that cannot be controlled
by the conventional seismic design (red). These events can be regarded as the “complementary set” being a setof events that are complementary to those controlled by the conventional seismic design. These are the target ofthe anti-catastrophe design.
Fig. 2 schematically illustrates the seismic performance of structures with and without anti-catastrophe
design. Structures with only conventional seismic design show sufficient performance up to the level 2 groundmotions, but damage could significantly increase for excessive seismic actions (blue broken line). On the other
hand, we could imagine an ideal structure for which damage does not increase for excessive external forces (redline). In the anti-catastrophe design, engineers will take measures with both hardware and software so that theactual performance of structures approaches to the red line.
While the “anti-catastrophe design” is a new concept, the working group noticed that the necessity to beprepared for unexpected events has long been recognized among diligent engineers. In addition, the seismic
design codes have been improved since the occurrence of the 2011 Tohoku earthquake and now we can finddescriptions about the preparedness of structures in the face of unexpected events in these codes. It would be2

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

meaningful to review the seismic design codes in Japan and to understand how these codes are trying to assess
the issue of the preparedness of structures in an unexpected event.
In order to contribute to the establishment of the “anti-catastrophe” design concept of structures, Japanesedesign standards for railway structures, highway structures, and port structures are reviewed in this article, withspecial reference to their recent trends. Design examples are presented in which “anti-catastrophe” designconcept is considered implicitly or explicitly both before and after the 2011 Tohoku earthquake. In addition, the“anti-catastrophe” design concept is discussed in the context of international trends of structural design.

Fig. 1 – The relationship between the conventional seismic design and the anti-catastrophe design

Fig. 2 – Seismic performance of structures with and without anti-catastrophe design

2. Railway structures
2.1 Principles of preparedness of structures to unexpected events
In the seismic design of structures in Japan, significantly intense ground motions have been adopted as the level2 design ground motions, referring to the near-source ground motions in Kobe during the 1995 Kobe earthquakeand other damaging ground motions including those from subduction earthquakes. However, it is important to3

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

acknowledge that, after all, the level 2 design ground motions are based on the judgment of a group of skilled
engineers and they do not represent the strongest possible ground motion from a physical point of view at thesite. Therefore, the level 2 design ground motions may be exceeded during the design working life of a structureirrespective of the method used to determine the level 2 design ground motion. This recognition is the important
starting point for the “anti-catastrophe design”.
The revised version of the seismic design standards for railway structures [2], published in 2012 after theGreat East Japan Earthquake, addresses these issues, stating “the possibility of the occurrence of a groundmotion exceeding the level 2 design ground motion cannot be denied”. Then the revised version states theprinciples of preparedness of structures in unexpected events, saying “because railway structures bear highly
public nature and their functionality is quite important for human life and social/industrial activities, in theseismic design of structures, in addition to considering safety and restorability, a structure should be designed sothat the structure or the structure-environment system does not exhibit catastrophic situation even in an
unexpected event”. These expressions constitute the basis for our definition of the “anti-catastrophe design”
stated in the introduction of this article, although the design standards for railway structures [2] do not use theterm “anti-catastrophe” explicitly. It is also stated in the design standard [2] that, because verification methods
have not been established for this purpose, the preparedness in unexpected events should rather be considered instructural planning.

2.2 Descriptions related to “anti-catastrophe design” in the design standards
We can find more detailed descriptions about the preparedness of structures in unexpected events in the design
standards for railway structures [2]. In the following, two examples are described.
It is well known that shear failure of a concrete structure is brittle and unfavorable compared to bending
failure. The design standards for railway structures [2] recommend a structure that fails in bending rather than inshear. Let us assume two types of structures that do not fail under the level 2 ground motion; however, one
exhibits bending failure and the other exhibits shear failure under a ground motion that exceeds the level 2
ground motion. If we do not have to consider the possibility of the occurrence of a ground motion exceeding thelevel 2 ground motion, there is no difference between these two types of structures. However, in fact, the level 2
ground motion could be exceeded. Therefore, the former structure is preferable. Thus, the above expression interms of the preferred failure mode can be regarded as related to the preparedness of a structure in an unexpected
event.
The design standards for railway structures [2] also recommend that the environment of a structure shouldadequately be planned so that it allows for rapid restoration of the structure when it is subject to earthquake
damage. In particular, based on past experiences of damaging earthquakes, the rapidity of the restoration islargely dependent on the availability of a service road or a space under elevated tracks. Therefore, the standards
recommend reserving an access route or a yard for the restoration work. The standards also recommend that thedamage to a structure should be restricted to a member or a portion of a structure for which inspection andrestoration can easily be carried out.

2.3 Recent efforts to improve preparedness of structures in unexpected events
After the publication of the latest version of the design standards for railway structures [2], more efforts havebeen made to improve the preparedness of structures in unexpected events. In the following, two examples aredescribed.
One example is the so-called “dead weight compensation mechanism” [3], which was recently proposedby the Railway Technical Research Institute (RTRI). The concept of this mechanism is shown in Fig. 3. The blue
columns in Fig. 3 are ordinary columns and the red columns are the “dead weight compensation columns”. The
ordinary columns undergo conventional seismic design for the level 2 ground motion. On the other hand, thedead weight compensation columns only bear the vertical forces and are free from the horizontal forces due tothe inertia force acting on the slab. Therefore, we could expect that the dead weight compensation columns
should remain intact even after the action of excessive seismic forces. Thus, even when the ordinary columns aredamaged and collapse as shown in Fig. 3, the dead weight compensation columns will support the slab.
4

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

Fig. 3 – Dead weight compensation mechanism [3]Table 1 – Feasibility study on the dead weight compensation mechanism [3]Type of structure

Bar arrangement of ordinary columns
Longitudinal bar

Transverse reinforcement

Ordinary structure

5-D32

D19@150

Structure with dead weight compensation mechanism

7-D32

D19@100

Nishimura et al. [3] investigated the feasibility of this mechanism for a rahmen elevated bridge with one
layer and 5 spans. According to the results, if four out of twelve ordinary columns are replaced with the deadweight compensation columns, for instance, horizontal forces acting on the ordinary columns increase and thestrength of the ordinary columns should be increased. However, this increase can be covered by only a small
number of additional longitudinal bars as shown in Table 1.
Another example is the control of the direction of structural collapse. In case of structural collapse, itsconsequences may largely be dependent on its direction. Saito et al. [4] proposed to control the direction of
structural collapse to prevent loss of lives, to avoid interrupting emergency transportation, and to reserve accessroutes or spaces for restoration (Fig. 4). The direction of structural collapse may be controlled by adequately
determining the relative strength of the members that constitute the structure [4].

5

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

Fig. 4 – Control of the direction of structural collapse [4]. Controlling the direction of collapse may contribute toprevent loss of lives (A), to avoid interrupting emergency transportation (B), and to reserve access routes orspaces for restoration (C).

3. Highway structures
3.1 Principles of preparedness of structures to unexpected events
The design specifications for highway bridges in Japan have been published in several volumes. The volumes I,
II, III, IV, and V are devoted to common aspects, steel bridges, concrete bridges, substructures, and seismic
design, respectively. The latest version was published in 2012.
Published after the 2011 Great East Japan Earthquake, the latest version of the specification involves
descriptions related to the principles of the preparedness of structures in unexpected events [5]. The specification
points out that failure of one member of a bridge may cause the collapse of the whole structure if the structure is
not appropriately designed. It requires the engineers to pay attention to this fact while designing the structures. It
should be noted that the statement is not specific to earthquakes but it applies to all other unexpected events. The
statement is accompanied by commentaries [5]. The followings are the essence of the commentaries.
In the design of bridges, various actions that could affect the structure during the design working life areconsidered. However, the specification admits that the bridges may be subjected to unexpected external loads
during the design working life and may be damage. It should be noted that, in the design of highway bridges inJapan, the level 2 design ground motion is considered, just as in the design of railway structures. Therefore, theabove statement is equivalent to the expression “the possibility of the occurrence of a ground motion exceeding
the level 2 design ground motion cannot be denied”, which is included in the seismic design standards forrailway structures [2] and discussed in 2.1. This recognition is important as the starting point for the “anticatastrophe design”.
The specification points out the importance of taking measures to avoid “extremely unfavorable situation”
in an unexpected event. Therefore, although the specification does not use the term “anti-catastrophe” explicitly,
one can conclude that the concept of “anti-catastrophe design” has already been introduced in the design
specifications for highway bridges in Japan. It should be noted that, if the bridge is closed for a long time for fearof collapse or the bridge is forced to be demolished, it is called an “extremely unfavorable situation” even when
the bridge has not actually collapsed.
The specification also admits that it is difficult to propose a unified criterion in terms of what kind of
measures should be taken, because this issue requires comprehensive judgment based on a consideration of other6

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

important aspects such as costs and workability. Therefore, the specification just recommends that the engineersconsider the possibility of unexpected events, and take measures whenever appropriate, instead of specifying
verification methods.

3.2 Unseating prevention device [6]When a highway bridge is subject to extremely large ground motions, a bearing failure may take place, resulting
in deck unseating. To prevent such an unfavorable situation, “unseating prevention devices” have widely beenused in the design of highway bridges in Japan [6]. Some of those devices actually succeeded in preventing deck
unseating in the past earthquakes. Fig. 5 shows an example of such device. The figure shows an unseating
prevention device installed at Ono Bridge, Miyagi Prefecture, Japan, after the July 26, 2003, Northern Miyagi
Prefecture earthquake (M6.4) [7, 8]. During the earthquake, all the bearings on the abutments and the pierssuffered significant damage such as shear failure of anchors. As a results, the girder displaced in the axial
direction 0.2 m at maximum. After the earthquake, tensile force was acting in the PC cable of the unseating
prevention device connecting the superstructure and abutment. Therefore, the investigation team concluded thatthe unseating prevention device efficiently prevented the unseating of the superstructure. As another example,
Fig. 6 shows an unseating prevention device installed at Kiyamagawa Bridge, Kumamoto Prefecture, Japan,
before and after the

Fig. 5 – Unseating prevention device installed at Ono Bridge, Miyagi Prefecture, Japan, after the July 26, 2003,
Northern Miyagi Prefecture earthquake [7, 8].

Fig. 6 – Unseating prevention device installed at Kiyamagawa Bridge, Kumamoto Prefecture, Japan, before (left)
and after (right) the April 16, 2016, Kumamoto earthquake.
7

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

April 16, 2016, Kumamoto earthquake (M7.3). Since the girder is slightly skew, concrete blocks were installed
to prevent excessive displacement in the longitudinal and transverse directions in preparation for bearing failure.
During the earthquake, all the steel bearings on the piers suffered significant damage such as failure of pin
connections. As a result, the girder hit the concrete blocks, but the device succeeded preventing unseating. In thecontext of this article, the unseating prevention device is one of the most typical devices for “anti-catastrophe
design”, because it is installed in preparation for unexpected events such as extremely large ground motions.
On the other hand, the design specification for highway bridges [6] also suggests some cases where theinstallation of the unseating prevention devises can be omitted. According to the specification, the installation
can be omitted for bridges where the displacement of the superstructure in the axial direction is restrictedbecause of structural characteristics. From a perspective of the “anti-catastrophe design”, such structures are
preferable, because their structural characteristics contribute to avoiding the unfavorable situations created bydeck unseating. Therefore, selecting one of these types of structure in the process of structural planning can be
regarded as one example of “anti-catastrophe design”.
According to the specification [6], the displacement of the superstructure in the axial direction is restrictedin the following cases.
1) A bridge with a continuous girder supported by abutments at both sides is one of the structures where theinstallation of the unseating prevention device can be omitted, because even if the bearings are damaged and thedisplacement of the superstructure in the axial direction occurs during an earthquake, the superstructure willsoon collide with one of the abutments, and further displacement will be restricted because of the reaction of theabutment and the backfill soil.
2) A bridge with a continuous girder supported by at least four elastic bearings or fixed bearings in the axial
direction as shown in Fig. 7 is one of the structures where the installation of unseating prevention device can beomitted, because this type of structure will exhibit sufficient redundancy. It should be noted that the inertia force
should uniformly be distributed over different bearings in this type of structure because, if the inertia force issupported only by a few bearings, the failure of the bearings is anticipated, which may result in a successive
failure of a larger part of the structure. According to the specification, the inertia force supported by one bearing
should not exceed 50 % of the total inertia force.

Fig. 7 – A bridge with a continuous girder supported by at least four elastic bearings or fixed bearings in theaxial direction3) A rahmen bridge rigidly supported by at least two piers as shown in Fig. 8 is one of the structures where theinstallation of the unseating prevention device can be omitted, because it is not realistic to expect a total ruptureof the rigid supports and the separation of the superstructure and substructure.

8

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

Fig. 8 – A rahmen bridge rigidly supported by at least two piers
The specification [6] also calls attention to some cases where the rotation of a deck may lead to unseatingof the deck. Fig. 9 shows curved bridges with different plan views. (a) shows an unfavorable plan view where
AB<AH1 and the rotation of the deck may lead to unseating of the deck. (b) shows a favorable plan view where
AB>AH2 and the rotation will be restricted due to the existence of neighboring decks or abutments. Therefore, inthe context of this article, selecting a plan view in (b) instead of (a) in the process of structural planning can be
regarded as one example of “anti-catastrophe design”.

Fig. 9 – Curved bridges with different plan views. (a) shows an unfavorable plan view where AB<AH1 and therotation of the deck may lead to unseating of the deck. (b) shows a favorable plan view where AB>AH2 and therotation will be restricted due to the existence of neighboring decks or abutments.

4. Port structures
4.1 Design tsunami
In light of the serious tsunami disaster during the 2011 Tohoku earthquake, the technical standards for port
structures in Japan [9] were partially revised in 2013 [10]. In the revised version, the term “design tsunami” was916th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

introduced for the first time. The design tsunami is defined as “a tsunami that has a low probability of occurrence
during the design working life of a structure and that will have a significant effect on the structure”. The design
tsunami should be determined based on past records or numerical simulations [10].
For the design tsunami, the port structures are intended to protect not only human life but also properties.
For this purpose, the concept of multiple protection is encouraged, where the effects of every structure including
breakwaters and tide embankments should be integrated and utilized for the protection. It is believed that,
although the original purpose of the breakwaters is to keep the calmness of the port for ordinary ocean waves,the breakwaters can contribute to reducing the tsunami energy efficiently depending on their distributions.
The performance verification for breakwaters or tide embankments for the design tsunami are basicallyconducted by applying a tsunami force and by assessing their stability against such failure modes as sliding,overturning, and instability of underlying ground. The applied force on the breakwater is dependent on theoccurrence of overflow, because overflow is allowed for a breakwater.

4.2 Tsunami exceeding the design tsunami
The design of breakwaters or tide embankments for the design tsunami mentioned above corresponds to theconventional seismic design shown in blue in Fig. 1. On the other hand, the design for a “tsunami exceeding thedesign tsunami”, which was also newly introduced in the technical standards for port structures in Japan in 2013[10], can be regarded as one example of “anti-catastrophe design”, in the context of this article.
Although the original purpose of the breakwaters is to keep the calmness of the port as mentioned in 4.1, it
is believed that the breakwaters can contribute to reducing the height of tsunami that arrives at the protection line
including tide embankments and to delay the arrival time. For example, according to the numerical simulation
conducted by the Port and Airport Research Institute [11], the Kamaishi Tsunami Breakwater contributed toreducing the tsunami height at the inner part of the bay by about 40 % and delaying the time of overflow at thetide embankments by about 6 minutes, although the breakwater finally collapsed. This amount of time will havea significant effect in assisting the tsunami evacuation.
For a tsunami exceeding the design tsunami, the port structures are intended to assist human evacuationand to reduce damage to properties as much as possible. For such a tsunami, of cource, the most important action
is evacuation. However, if the breakwater is robust enough and it takes sufficiently long time before its collapse,
the breakwater will be able to assist the evacuation activity.
From such a point of view, the technical standards for port structures in Japan partially revised in 2013[10] addresses the performance requirements of a breakwater for a tsunami exceeding the design tsunami. The
revised technical standards states: “In terms of the performance requirement of a breakwater for which theconsequence of failure is significant including loss of life and property or significant negative effects to socioeconomic activities, when it is subject to a tsunami exceeding the design tsunami, the collapse of the structure
should be delayed as much as possible”. For a tide embankment with equivalent importance, similar
performance requirement is stated in the revised technical standards.
For the purpose of realizing a robust breakwater, various methods have been proposed including
embankment widening and scour protection. For the verification of the methods, hydraulic model tests andnumerical simulations are used.
As mentioned above, in the design for a “tsunami exceeding the design tsunami”, not only theperformance of the structure itself but also of the structure-environment system, which is the tsunami-affected
region including the breakwater in this case, is considered as a system. Then, based on the expectedconsequences, possible measures are taken. Therefore, the design for a “tsunami exceeding the design tsunami”
is one example of a true “anti-catastrophe design”, in the terminology of this article. In the future, if the positiveeffects of various measures to improve the breakwater robustness are evaluated through tsunami inundation
simulations and evacuation simulations in terms of their contribution to assisting evacuation activities, theeffectiveness of the measures will be recognized more widely.
10

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

5. Discussion and Conclusions
As mentioned above, in light of the serious tsunami disaster during the 2011 Tohoku earthquake and thesubsequent severe accident at the Fukushima-Daiichi Nuclear Power Plant, the preparedness of infrastructures
such as railway structures, highway structures and port structures in unexpected events became a big issue
among civil engineers in Japan. The authors formed a working group to discuss this issue within the frameworkof the Earthquake Engineering Committee, the Japan Society of Civil Engineers.
In the conventional seismic design of these structures, basically two kinds of design ground motions,
namely, the level 1 and 2 design ground motions are considered and the structures are designed so that they
fulfill respective performance requirements through verification. In particular, significantly intense groundmotions from shallow crustal and subduction earthquakes have been considered as the level 2 design groundmotions. However, it is still necessary to consider the performance of structures under unexpected events and its
consequences, mainly because of our insufficient knowledge of natural phenomena and of the performance ofstructures itself. Therefore, the working group proposed a new design concept called the “anti-catastrophe designconcept”. In this concept, a structure is said to be “anti-catastrophe” when the structure or the structureenvironment system does not exhibit catastrophic situation even in an unexpected event. The working group has
started developing a framework for the design of structures based on this concept.
While the “anti-catastrophe design” is a new concept, the working group noticed that the necessity to beprepared to unexpected events has long been recognized among diligent engineers. In addition, the seismic
design codes have been improved since the occurrence of the 2011 Tohoku earthquake and now we can finddescriptions about the preparedness of structures in unexpected events in these codes. In order to understand how
these codes are trying to assess this issue and to contribute to the establishment of the “anti-catastrophe” designconcept of structures, the design standards for railway structures, highway structures, and port structures in Japanare reviewed, with special reference to their recent trends.
In all of these codes, the necessity to consider the performance of structures under unexpected events andits consequences are recognized. For the railway structures, devices have been developed for the anti-catastrophe
design including the “dead weight compensation mechanism”. For the highway structures, “unseating prevention
devices” have widely been used in the design of bridges. On the other hand, the design specification for highway
bridges suggests some preferable structures where the displacement of the superstructure in the axial direction isrestricted and unfavorable situations such as deck unseating can be avoided. For the port structures, efforts arebeing made to improve the performance of breakwaters after they are affected by extreme tsunamis.
One of the most important ingredients of the “anti-catastrophe design” is to understand the performance ofa structure or a structure-environment system under extreme external forces to understand its consequences. In
this respect, the “anti-catastrophe design” is oriented in the same direction as the “risk-informed design”
proposed in the revised version of ISO2394 [12], where the engineers are requested to evaluate the consequenceof structural failure. However, as mentioned above, the Japanese engineers seem to put more emphasis on thedevelopment of measures or devices to cope with this issue, probably because “the unexpected events” are much
more realistic in Japan than in any other country on the globe. In addition, some of the devices have alreadyperformed well during past large events.
It should be noted that our knowledge is quite limited in terms of the performance of a structure or astructure-environment system subject to extreme events. So far, our main concern was to evaluate theperformance of structures subject to “design ground motions”. Thus, less attention has been paid to theperformance of structures subject to a strong ground motion exceeding the design ground motions. Obviously
more effort is needed to understand the performance of structures under extreme events to develop reliablemeasures or devices. To this end, every kind of available tools should be used. For example, model tests andnumerical simulations could be useful, as they have been useful in the study of robust breakwaters in the field ofport engineering.
On the other hand, it is not reasonable to think that the performance of such devices or measures could
always be evaluated quantitatively. Sometimes, other human abilities such as intuition and insight could be
useful in developing measures and devices. As an example, although we do not know the detailed stress historyof unseating prevention devices during an earthquake, they have widely been used in the design of highway
bridges in Japan and some of those devices have performed well in the past earthquakes.
11

16th World Conference on Earthquake Engineering, 16WCEE 2017
Santiago Chile, January 9th to 13th 2017

After all, we should mobilize all kinds of human ability, ranging from intuition or insight to moresophisticated engineering skills, to cope with the issue of the preparedness of structures to unexpected events.

6. Acknowledgements
The authors would like to thank the members of the “anti-catastrophe design” working group, the Earthquake
Engineering Committee, the Japan Society of Civil Engineers, for fruitful discussions.

7. References[1] Honda R, Akiyama M, Kataoka S, Takahashi Y, Nozu A and Murono Y (2016): Seismic design method to consider“anti-catastrophe” concept - A study for the draft of design codes. 16WCEE, Santiago, Chile.
[2] Railway Technical Research Institute (2012): Design Standards for Railway Structures and Commentary (Seismic
Design), Maruzen (in Japasese).
[3] Nishimura T, Murono Y, Motoyama H and Igarashi A (2015): Study on seismic performance and feasibility of the“dead weight compensation mechanism” for improving “anti-catastrophic performance”. The 35th JSCE Earthquake
Engineering Symposium, Tokyo, Japan (in Japanese with English abstract).
[4] Saito M, Murono Y and Motoyama H (2015): Anti-catastrophe mechanism by controlling the direction of structural
collapse. The 70th JSCE annual meeting, Okayama, Japan.
[5] Japan Road Association (2012): Design Specifications for Highway Bridges, Volume I, Common Aspects (in Japasese).
[6] Japan Road Association (2012): Design Specifications for Highway Bridges, Volume V, Seismic Design (in Japasese).
[7] Damage Investigation Team, National Institute for Land and Infrastructure Management and Public Works Reseacrh
Institute (2005): Preliminary report on the damage due to the July 26, 2003, Northern Miyagi Prefecture earthquake,
Civil Engineering Journal, 45 (9), 10-15 (in Japanese).
[8] Japan Road Association (2006): Earthquake Disaster Prevention Handbook for Highways – Proactive Measures - (inJapasese).
[9] Ports and Harbours Association in Japan (2007): Technical Standards for Port Structures (in Japanese).
[10] Ports and Harbours Bureau, Ministry of Land, Infrastructure, Transport and Tourism, Japan (2013): Revision in termsof the design tsunami and related performance requirements, http://www.mlit.go.jp/common/001012831.pdf (inJapanese).
[11] Takahashi S et al. (2011): Urgent survey for 2011 Great East Japan earthquake and tsunami disaster in ports and coasts,
Technical Note of the Port and Airport Research Institute, No.1231 (in Japanese with English abstract).
[12] International Standardization Organization (2015): ISO2394 – General principles on reliability for structures.

12