T T

Where b is the width of the building, and J is the aspect ratio h b. Considering a building of height 80 m and width 20 m, then J 4. The fundamental period of the building is T 1.8 s. If the building is sited on soils for which the shear wave velocity vs 100 m s, then from equation (5.37) the effective period of the structure as modified by the soil is found to be T T 1.73, i.e. T 3.11 s. Clearly, this soft soil (Table 5.1) has a substantial effect on the vibrational characteristics of the...

855 Rocking structures

As well as the methods described in the preceding sections, the flexibility required to reduce seismic response may be obtained by allowing part of the structure to lift during large horizontal motions. This mechanism is referred to variously as uplift, rocking, or stepping, and involves a discontinuity of contact between part of the foundations and the soil beneath, or between a vertical member and its base. The good performance of many ordinary structure in very strong ground shaking can only...

1 V

G is the shear modulus for the soil, where G E 2(1 + v is Poisson's ratio for soil, p is mass density for soil, R is radius of footing, B, L, are the plan dimensions of rectangular pads, and fix, fiz, 3, are coefficients given in Figure 5.13. *The properties come from Clough and Penzien (1993). fFor torsional spring stiffnesses of rectangular footings see Newmark and Rosenblueth (1971, p. 98). Figure 5.13 Coefficients fix, fiz and fy for estimating spring stiffness of rectangular footings as in...

24

In Table 7.1 As with mean damage ratios Drm due to shaking, fire damage models are region specific, depending on many factors which include the separation of buildings and other flammable materials, incidence of ignition sources, terrain and vegetation, the climate and wind regime, and post-earthquake operational fire-fighting resources. These factors were first developed for Californian studies by Scawthorn (1987). In Table 7.2, it can be seen that the fire risk for non-domestic buildings is...

Unit

Figure 10.37 Alternative column confinement details of different effectiveness (see text) (after Tanaka et al, 1985) where the ratio of the flexural tension reinforcement pw is expressed in terms of Vc (1 + 12Nu Af'c )vb (10.50) vc 0.27 + Nu 4Ag (MPa) (10.51) When the force load Nu produces tension, its value in equations (10.50) and (10.51) must be taken as negative. (2) In regions of plastic hinges Equations (10.53) and (10.54) apply when the axial load Nu results in compression. When Nu...

2

Figure 4.18 fo estimated from the spectrum of the San Fernando earthquake of 9 February 1971, Ml 6.4 at the Pacoima Dam site (adapted from Hanks, 1982) Figure 4.18 fo estimated from the spectrum of the San Fernando earthquake of 9 February 1971, Ml 6.4 at the Pacoima Dam site (adapted from Hanks, 1982) where G is a ramp function which increases linearly from zero at t 0 to unity at t T (where T is the rise time), and u is the final displacement. The rise time may be determined directly if the...

D

Figure 6.20 Mean damage ratio and its 95 confidence limits for household contents in houses on piled and concrete foundations and on four ground classes at intensity MM7.5 (Greymouth, New Zealand) (from Dowrick et al., 2003) Drm for contents of all houses (with piled and concrete foundations) on Ground Classes C and CD. Dowrick et al. (2003) found that at intensity MM7.0, Drm for the contents of houses situated on Ground Class D was less than for those on Ground Class, similar to the trend for...

B

Figure 2.4 Seismic cross-section through the North Island of New Zealand, showing locations of earthquake foci (reproduced with permission from G.R. Stevens, 1980) Figure 2.4 Seismic cross-section through the North Island of New Zealand, showing locations of earthquake foci (reproduced with permission from G.R. Stevens, 1980) study (Figure 2.5), which relates the shear strains of the shear belt referred to above to large historical earthquakes. It is believed that the fault forming the plate...

E

Figure 4.13 Magnitude-frequency relationship for earthquake occurrence For any given region if enough data is available a plot of M against log N can be made, and the best-fit line of the form of equation (4.18) can be determined by regression analysis. To get the best results, allowance should be made for both incompleteness of the data (Kijko and Sellevoll, 1989) and magnitude uncertainties (Rhoades, 1996). Although there are arguments for expressions other than equation (4.18) (e.g....

20 10 0

Figure 3.2 Conceptual development of Turnagain Heights landslide, Anchorage, Alaska, due to liquefaction of sand lenses (after Seed, 1968) (reproduced by permission of the American Society of Civil Engineers) (9) The water content of the soil is an important factor in site response. This applies not only to sloping soils as mentioned above, but liquefaction may also occur in flat terrain composed of saturated cohesionless soils (Section 5.2.2). Classical examples of failures of this type...

150

Luggate schist fan and greywacke outwash gravel Seismic refractor in Q105 Located 20 m deeper than inferred from seismic profile wash creek sediments A to Faults identified in G trenches Scale H V 1 2000 Seismic refractor in Q105 Located 20 m deeper than inferred from seismic profile p Inferred synthetic fault 'dip shown 45 N.W.

136 Retrofitting Equipment and Plant

Equipment and plant vary enormously in their inherent vulnerability in earthquakes. As discussed in Section 6.3.3, Fragile equipment has been shown to be many times more vulnerable than Robust equipment, so there is considerable potential for reducing damage by retrofitting Fragile or Medium equipment. An example of such retrofitting comes from the Haywards HVDC Converter Station in the Wellington region of New Zealand. Here the AC Filter Capacitor Banks, made essentially of brittle porcelain,...

1

Figure 10.39 Models of the two modes of transfer of horizontal shear in a beam-column joint (after Part 2 of NZS 3101 (1995)) (Reproduced by permission of Standards New Zealand) Figure 10.40 Detail of a beam-column joint in a precast concrete moment-resisting frame (after NZCS, 1998) Figure 10.40 Detail of a beam-column joint in a precast concrete moment-resisting frame (after NZCS, 1998) whereby the beneficial effects of the axial compression load acting on the column above the joint may be...

K 0778

The location and maximum moment in the pile section are given by where Imh aKb, a 0.6.f, and b 0.17f-03. If IMH is greater than 8, a value of 8 is used. (iii) Non-linear lateral displacements of a single 'long' pile For estimating the effect of local soil failure at the pile soil interface, Davies and Budhu (1986) proposed a modification factor to be applied to the elastic behaviour model. Thus for a free-head pile, the pile head displacement, rotation and maximum moment are found from where...

C D

Figure 9.6 Zone of densification of potentially liquefiable soil required beneath and surround- soils, the area densified needs to be extended to a zone within an angle of 30 -45 away from the base of the structure (Iai et al., 1988), as shown in Figure 9.6. The strength and stiffness of a soil deposit is sometimes improveable by installing in it discrete elements of other materials, such as concrete, steel, timber or dense gravel. For countering liquefaction these elements are generally in the...

13

(4) Includes 27 injured who died (5) Includes one injured who died (6) Includes 28 injured who died. (4) Includes 27 injured who died (5) Includes one injured who died (6) Includes 28 injured who died. From Table 6.6, it can be seen that casualties have occurred in earthquakes of a wide range of magnitude (5.6-8.2), and from Modified Mercalli intensity MM7 to MM10. Thus intensity MM7, which is the effective threshold of structural damage for New Zealand construction is correspondingly the...

Info

* Representative of San Francisco Bay area. * Representative of San Francisco Bay area. such as the restraint imposed by sides of valleys on alluvial deposits, and by properly judging the appropriate depth H to bedrock. For example, for using equation (5.8) bedrock may be defined as a low strain shear wave velocity of about 700 m s. In the Lake Zone of Mexico City, the depth to the stiff soil layer which constitutes effective bedrock ranges up to about 60 m, and at this location the superficial...

131 Earthquake consequences and their acceptability

The primary consequence of concern in earthquakes is of course human casualties, i.e. deaths and injuries. According to Steinbrugge (1982), the greatest known number of deaths that have occurred in a single event is 830,000, in the Shaanxi, China, earthquake of January 24,1556. Thus the number of casualties in any given event varies enormously, depending on the magnitude, location and era of the earthquake. This is illustrated by a selection of 26 of the more important earthquakes of the 20th...

53 Seismic Response of Soil Structure Systems 531 Introduction

The importance of the nature of the sub-soil for the seismic response of structures has been demonstrated in many earthquakes. For example, it is clear from studies of earthquakes that the relationship between the periods of vibration of structures and the period of the supporting soil is profoundly important regarding the seismic response of the structure. An example from Mexico City is given in Section 3.2, item (2). In the case of the 1970 earthquake at Gediz, Turkey, part of a factory was...

76 Planning for Earthquakes

Planning for earthquakes refers to a range of activities, which involve generally complex issues, particularly Planning of disaster emergency response. Planning of economic response. Planning of social response. Damage scenarios based on damage ratios, such as in Figure 7.1, provide information on the potential outcomes of future earthquakes which is highly relevant to planning of land-use, and of economic and social response to earthquakes. Such damage maps highlight the existence and extent...

121 Introduction

A large part of the damage done to buildings by earthquakes is non-structural. For instance, in the San Fernando, California, earthquake of February 1971, a total of 500 million worth of damage was done to the built environment of which over half was non-structural. The importance of sound anti-seismic detailing in earthquake areas should need no further emphasizing. The choice of a suitable structural form is crucial, involving full collaboration at conceptual design stage between architects...

442Types of fault

The characteristics of strong ground motion are strongly influenced by the type of faulting. There are four main types of fault that should be considered in the study of destructive earthquakes (1) Subduction zone interface (underthrust) faults (Figure 4.3(a)). These result from tectonic sea-bed plates spreading apart and thrusting under the adjacent continental plates, a phenomenon common to much of the circum-Pacific earthquake belt (2) Compressive, overthrust faults (Figure 4.3(b))...

00 01 02 03 04 05 06 07 08 09 10

Figure 4.43 Probabilistic seismic hazard map of New Zealand, showing peak ground accelerations with a 10 probability of exceedance in 50 years, derived using Stirling et al. (2000) (M Stirling, personal communication, 2001) down the South Island where a number of long, very active faults are located (see Figure 4.4). Figure 4.43 is taken a stage further in Figure 4.44(b), where it is in the form of a seismic hazard zoning map for use in a loadings code. Here it is compared with the 1992 code...

636 Upper and lower bounds on vulnerability

The mean damage ratio data for buildings and equipment from the various studies referred to above are plotted in Figure 6.21, and lines representing approximate upper and lower bounds to the data have been drawn. It is interesting to note that the most robust buildings and equipment have similar levels of vulnerability, and the same is true for fragile equipment and brittle buildings. The improvement in vulnerability of buildings from the 1960s to the 1980s is very apparent in this plot. The...

00

Models showing spatial distribution of longer period motion resulting from near fault directivity. Maximum magnitudes of the horizontal displacement and velocity vectors at each point on the ground surface. The solid line indicates the vertical projection of the fault plane on to the ground surface, and the hollow circle identifies the epicenter. The south-southeast slip direction (rake angle of 105 ) creates the asymmetry in the east-west direction. Fault dip 23 , top of fault 8 km deep (from...

3

Plan on column segment of foundation Plan on column segment of foundation x axis (direction of T horizontal load) x axis (direction of T horizontal load) Figure 5.12 Cooling tower with soil properties approximating a layered half-space, represented by a two-dimensional model of springs and dashpots These springs give a rotational stiffness

3504

Flexure and axial load 354-5 singly reinforced sections 347-9 in situ design and detailing 365-9 required ductility (robustness) 346-7 Cone penetrometer tests (CPT) 36, 37 Configuration of construction 253 Confinement effect on ductility 350-2 reinforcing (columns) 370-2 see also Transverse steel Connections in diagonally braced frames 342 in precast concrete 378-85 adjacent wall units 385 bases and columns 378-9 columns and beams 380-1 floor and roof units 381, 383 -4 floors and walls 381-3 in...

635 Microzoning effects on vulnerability functions

Microzoning effects in very strong shaking (MM10) The effects of different ground conditions on the response of structures, referred to as microzoning effects, are functions of both frequency and amplitude of vibration. The dependency on amplitude has been shown in Peak Ground Acceleration (PGA) terms by Idriss (1990), such that PGAs on soils are greater than PGAs on rock at low amplitudes, while the reverse is true at high amplitudes. This occurs because the weaker the soil is, the lower is...

62 Qualitative Measures of Vulnerability

Vulnerability of different classes of construction has long been described in words in the subjective intensity scales. This is illustrated in Table 6.1 where the degree of damage to six classes of construction is described for seven Modified Mercalli intensities (MM6-MM12). An aspect of this table that is worth noting is the speculative nature of intensities MM11 and MM12. The author knows of no verified instances of Earthquake Risk Reduction D.J. Dowrick 2003 John Wiley & Sons, Ltd ISBN...

5

Figure 4.32 Comparison of spatial patterns of ground motions (a) 1994 Northridge earthquake recorded intensities, (b) Simplest point source model, (c) shortest distance to planar source, (d) elliptical model, and (e) uniformly distributed planar asperity source classes considered in the models. It is of course normal to make the assumption of asperities when modelling future events, as in general little is known about asperities prior to any given earthquake. In terms of practicality and...

15 1530 615 1530

When using the results of penetration tests for assessing the condition of granular soils they may in some cases be used directly or else indirectly, i.e. after conversion to relative density. As the various penetrometer tests yield different numerical results for the same soils, the exact type of equipment used in each case must be known and appropriate conversions made where necessary for assessing results. For example Schmertmann (1970), related the static cone penetration resistance, Qc (kg...

1w

However, this value is only three quarters of that given by the half-space rocking spring formula In these circumstances, the stiffness value for the vertical springs will need to be chosen to give a conservative result depending on the nature of the loading. This will usually be done by increasing kzi so that the value of equates to the half-space solution. In some cases, it may be possible to equate the vertical and rotational stiffness criteria by locating the vertical springs on an...

Index

As design earthquakes 101-2, 109-11 of real earthquakes 105-6, 109 and response spectra, sources of 105-6 simulated 106 synthetic 109-11 Accelerograph 75, 430 Acceptable risk 5, 100 Added mass of soil 148, 156 Adhesion values for foundations 292 Adobe 394 Advocacy 10 Aftershock epidemic-type (ETAS) 71 power-law decay of 68 Alaska 1964 earthquake, Great 30, 31, 240 Allowable bearing pressure on soils 291 Alluvium see Soil Amplification (in soil) 131, 137, 142, 144 Analysis, method of, for...

05

Steel plated L Anchor bolt Neoprene lining 11.15 Combined earthquake mountings and vibration isolation for machine bases and pipework (after Berry, 1972) close to common building periods and the resulting resonance would cause large movements, considerable noise and possible failure. This can be avoided by the provision of horizontal restraints or by the use of two hangers in a V-formation. As noted in Section 11.3.3, specially designed energy absorbing supports for pipework are an aseismic...

074 090

Figure 4.29 Isoseismal dimensions and shapes predicted by the attenuation model of Dowrick and Rhoades (in prep, 2003b), for earthquakes of various source parameters. The ratio b a is seen to increase with (i) source distance, (ii) depth, and (iii) decreasing magnitude expression from Dowrick and Rhoades (1999) a 102( -A1-A2Mw-A4hc) A3 - d2 - h2 1 2 (4.29) where hc is the depth to the centroid of the fault rupture, ht is the depth to the top of the rupture and I is the intensity of the strength...

J

End block if required, or anchor in column Detail 10.8 Site mortared and post-tensioned Connections between precast floors and walls The following typical details (Details 10.9-10.12) must be designed for the forces acting on the joint under consideration. Member reinforcement is not shown. Connections between adjacent precast floor and roof units The following typical details (Details 10.13-10.16) must be designed for the forces acting on the joint under consideration. Floor slabs should be...

10

Figure 10.14 Stiffness of braced frames varying with eccentricity (after Hjelmstad and Popov, 1983) The geometry of the inelastically deformed EBF bay shall be such that the rotation angle between a beam and active link 9p for active links not attached to columns, shall not exceed the following 6p 0.09 radians for e < 1.6Msp Vw dp 0.045 radians for e < 3Msp Vw 9p is determined by interpolations for 1.6Msp Vw < e < 3Msp Vw, where Msp is the nominal plastic moment capacity. For active...

Note to 1996 Nz Mm Scale

Items marked * in the scale are defined below. Construction types Buildings Type I (Masonry D in the NZ 1965 mm scale) Buildings with low standard of workmanship, poor mortar, or constructed of weak materials like mud brick or rammed earth soft storey structures (e.g. shops) made of masonry weak reinforced concrete or composite materials (e.g. some walls timber, some brick) not well tied together. Masonry buildings otherwise conforming to buildings Types I III, but also having heavy...

Bfv

Where E is Young's modulus and v is Poisson's ratio. In the absence of any more specific data, low strain values of E may be taken from Table 5.3. Values of Poisson's ratio from Table 5.4 may be used in the above formula. Table 5.3 Typical modulus of elasticity values for soils and rocks Table 5.3 Typical modulus of elasticity values for soils and rocks

837 Choice of construction materials

Reliability of construction in earthquakes is greatly affected by the materials used for the constituent elements of structure, architecture, and equipment. It is seldom possible to use the ideal materials for all elements, as the choice may be dictated by local availability of local construction skills, cost constraints, or political decisions. Purely in terms of earthquake resistance the best materials have the following properties (2) high strength weight ratio (5) ease in making full...

443Degree of fault activity

Active faults include any faults which are considered capable of rupturing in the future. Because the amount and frequency of movement can vary enormously, it is important Figure 4.3 The main fault types to be considered in the study of strong ground motion (adapted from Housner, 1973) Figure 4.3 The main fault types to be considered in the study of strong ground motion (adapted from Housner, 1973) to be able to estimate the degree of activity likely to be exhibited by any fault in the region...

135 Retrofitting Structures

The retrofitting of a structure involves improving its performance in earthquakes through one or more of Increasing its strength and or stiffness. Reducing the input seismic loads. This may be done through modifications to one or more of Joints between structural elements. By way of example, three ways of improving the performance of weak or brittle columns suggested by Park (2001) are illustrated in Figure 13.3. These comprise (a) Adding reinforced concrete jackets, either as a full surround,...

Dd

Butt weld top and btm plates 1 s filler plate 31 2 x 3 x 3 s Z welded to column (2) A fillet-welded joint using flange plates. (3) A joint using high-strength bolts and flanges plates. In the tests it was found that the butt-welded joints were superior to the other two types in terms of total energy absorption. In the bolted joints, the hysteresis loops were reduced in area considerably by slippage, although the use of smaller than normal oversize holes reduced this effect. All the joints...

Yielding Of Steel In Singly Reinforced Be Occurs In

Under Reinforced Section

Required ductility (robustness) of concrete structures Referring again to objective (c) above, the degree to which ductility should be enhanced is debatable. Until the 1990s, research and codes had rightly been preoccupied with overcoming the excessive brittleness and unreliability of ill-reinforced concrete. However, there may have been too much emphasis of creating ductility for ductility's sake. The high cost of design and the complexity of some of the reinforcement of highly ductile...

002

Figure 6.18 (a) Mean damage ratio and its 95 confidence limits for single storey weatherboard houses, excluding chimney damage, at intensity MM8.5 (Westport, New Zealand) for two types of foundation and two ground classes, in the 1968 Inan-gahua earthquake (b) mean damage ratio and its 95 confidence limits for single storey weatherboard houses, including chimney damage, at intensity MM8.5 (Westport) for two types of foundation and two ground classes, in the 1968 Inan-gahua earthquake (from...

22 Global Seismotectonics

On a global scale, the present-day seismicity pattern of the world is illustrated in general terms by the seismic events plotted in Figure 2.1. Most of these events can be seen to follow clearly defined belts which form a map of the boundaries of segments of the earth's crust known as tectonic plates. This may be seen by comparing Figure 2.1 with Figure 2.2, which is a world map of the main tectonic plates taken from the highly understandable book on the theory of continental drift by Stevens...

S

Figure 4.40 Set of simulated input accelerograms and response spectra for a magnitude 7.0 earthquake with a closest distance to the causative fault of 50 km (after Valera and Donovan, 1973) distant events because of the greater long-period content of such events, while short-period structures designed to the same hazard level may be more sensitive to smaller, closer events. To further illustrate the point, Kuala Lumpur in Malaysia is located at the rather remote distance of about 400 km from...

343 Laboratory tests relating to dynamic behaviour of soils

A brief description of the nature, applications and limitations of the laboratory tests relating to the dynamic behaviour of soils, as summarized in Tables 3.2 and 3.3 is set out below. This soil property is related to the liquefaction of saturated cohesionless soils as discussed in Section 5.2.2. As the test for its determination is a standard laboratory procedure, it will not be described here. Although a number of classifications of grain size and standard sieves exist, correlations are...

Enlarged Connection Detail

Continuity bars welded to M.S. plate Continuity bars welded to M.S. plate Detail 10.16 Site welding and mortaring. Lapping steel plate bent on site to suit differential camber of adjacent precast units Connections adjacent precast wall units The following typical details (Details 10.17-10.22) should be designed for the forces acting on the joint under consideration. Great problems occur in producing a ductile and easily-erected precast shear wall, and no universal solution has as yet been...

853 Seismic isolation using flexible bearings

The most commonly used method of introducing the added flexibility for seismic isolation is to seat the item concerned on either rubber or sliding bearings. The energy dissipators (dampers) that must be provided may come in various forms. For use with standard bridge-type bearings made of rubber or sliding plates, any of the energy dissipators mentioned in Section 8.5.6 may be suitable. In addition, all-in-one devices, incorporating both isolation and damping, are used, namely lead-rubber and...

Hmo

Detail 10.20 Site welded and concreted full separation difficult to achieve, and some interaction of frame and cladding through bending of the connections may have to be accepted. Ductile behaviour of the cladding and of its connections to the structure is most important in such cases, to ensure that the cladding does not fall from the building during an earthquake. In stiff (shear wall) buildings the storey drift will generally be small enough to significantly reduce the problem of detailing...

References

Aguilar J, Juares H, Ortega R and Iglesisas J (1989) Statistics of retrofitting techniques in reinforced concrete buildings. Earthquake Spectra 5(1) 145-52. Applied Technology Council (1996) ATC 40 The Seismic Evaluation and Retrofit of Concrete Buildings. 2 volumes. Redwood City, USA. Bell DK and Davidson BJ (2001) Evaluation of earthquake risk buildings with masonry infill panels. Paper No 4.02.01. Technical Conference of NZ Soc for Earthq Eng, Wairakei, New Zealand. Bertero VV, Anderson JC...

Vfy Cladding

Figure 10.41 Schematic illustration of supports for precast concrete cladding fully separate from frame action Official recommendations for seismic design of prestressed concrete Some organizations interested in the use of prestressed concrete have published seismic design recommendations. For example, the FIP (1977) in addition to the New Zealand concrete code (NZS 3101, 1995), gives guidance on this subject. In contrast, the major USA concrete codes only discuss prestressed concrete in...

832 Simplicity and symmetry

Earthquakes repeatedly demonstrate that the simplest structures have the greatest chance of survival. There are three main reasons for this. First, our ability to understand the overall behaviour of a simple structure is markedly greater than it is for a complex one, e.g. torsional effects are particularly hard to predict on an irregular structure. Secondly, our ability to understand simple structural details is considerably greater than it is for complicated ones. Thirdly, simple structures...

1043 Reliable seismic behaviour of masonry structures

For obtaining reliable seismic response behaviour, the principles concerning choice of form, materials and failure mode control discussed in Section 8.3 apply to masonry structures, while further factors specific to masonry are discussed below. The wide range of masonry products, of clay and concrete types, means a wide range of material behaviour and hence of seismic reliability. Probably the most reliable type is reinforced hollow concrete blocks, which have been more studied than other...

I

Figure 6.9 Vulnerability measures for domestic property from the Inangahua earthquake compared with those from other earthquakes (a) Drm for houses, (b) Drm for contents, (c) Percentage of houses damaged, and (d) Percentage of contents parcels damaged (from Dowrick et al 2001) Figure 6.10 Plot of damage ratios for buildings versus contents for the MM9 zone of the 1987 Edgecumbe, New Zealand earthquake showing zero correlation, although Dr (buildings) Dr (contents) (from Dowrick, 1991)...

Cc

Figure 10.15 Beam-column connections with major axis column bending tested by Popov and Pinkney (1969). (a) Butt-welded beam-column joint (b) fillet welded beam-column joint (c) bolted beam-column joint Figure 10.15 Beam-column connections with major axis column bending tested by Popov and Pinkney (1969). (a) Butt-welded beam-column joint (b) fillet welded beam-column joint (c) bolted beam-column joint

12hd20

Figure 10.35 Elevation of a column in a ductile moment-resisting frame, showing splice located out of plastic hinge zone at column base reinforcement in the form of links should be added, especially where high shears exist, to help to confine the concrete in the development length. It is especially desirable to avoid anchorage bars in the 'panel' zone of beam-column connections. Large amounts of the reinforcement should not be curtailed at any one section. The minimum bend radius depends upon...

33 Ground Classes and Microzones

As soil types and thicknesses, and to a lesser extent rock, vary widely from site to site in a region and worldwide, many different ways of classifying sites exist. Fortunately as knowledge has grown in recent years of site response to earthquakes, there has been Total number of records analysed 104 Total number of records analysed 104

105

(1) Unclad refers to open industrial frameworks (perhaps with web grating steel flooring or platforms). Clad refers to most other structures such as offices. (1) Unclad refers to open industrial frameworks (perhaps with web grating steel flooring or platforms). Clad refers to most other structures such as offices. are conducted at low strain rates of about 10-3 s. Under seismic loading conditions in short period structures local strain rates may be in excess of 1.0 s, causing increases in fy of...

61 Introduction

To manage and minimize risk in future earthquakes, by design, planning and retrofitting, we need to understand and evaluate the earthquake vulnerability of the built and natural environments. This is best done by developing models by studying damage in past earthquakes, and quantifying the data on damage to a much greater degree than that which is possible in earthquake reconnaissance reports, or that given in the excellent book by Steinbrugge (1982). Earthquake damage to the built environment...

06

Sway Bracing Civil Engineering

Where Fac is the maximum compressive stress as a function of the slenderness ratio, calculated on a permissible stress basis, and As is the sectional area of the member. Where uniaxial bending occurs about the major principal axis design bending moment M* should satisfy where the strength reduction factor, and Mrx the nominal section moment capacity, reduced by axial force (tension or compression), Msx(1 (N* Ns)), where N* is the design axial force, Ns is the nominal section capacity for axial...

836 Appropriate stiffness

In designing construction to have reliable seismic behaviour, the design of structures to have appropriate stiffness is an important task, often made difficult because so many criteria, often conflicting, may need to be satisfied. The criteria for the stiffness of a structure fall into three categories, i.e. the stiffness is required (1) To create desired vibrational characteristics of the structure (to reduce seismic response, or to suit equipment or function). (2) To control deformations (to...

51Introduction

This chapter is principally concerned with the determination of seismic motions, stresses, and deformations necessary for detailed design. The design earthquake (Chapter 4) is applied to the soil and or the proposed form and materials of the structure (Chapter 8). In earthquake conditions the relationship should ideally be analysed as a structural continuum. Although in practice this is seldom feasible, each of the parts should be seen as part of the whole when considering boundary conditions....

Dso

Figure 11.10 Belleville washer damper arrangement for the earthquake protection of equipment (from Pham and Hoby, 1991) At the other end of the size scale, for small items of equipment Belleville washers provide an inexpensive and simple means of damping seismic motions. As can be seen in Figure 11.10, these washers are conical spring washers, which are designed to achieve A shift in the natural period of the equipment they support to outside the range where the ground acceleration is...

1038Columns

The design notes given in this section are aimed primarily at columns which form part of ductile moment-resisting frames. Columns in other situations, such as (1) trapped spandrel columns in wall frame systems, (2) columns in flat slab structures, and require specific consideration, as outlined by Selna et al. (1980). Other general design requirements for columns are as follows (4) The minimum width of the compression face of a member should be 200 mm. (5) The minimum content of longitudinal...

48 Faults Hazard and Design Considerations 481 Introduction

Intuitively the thought of building across an active fault is alarming, and obviously in general it is best avoided. However, in some circumstances structures can safely ride a fault rupture. For example, in the 1972 Managua earthquake the Banco Central de Nicaragua was astride a fault which moved 17 cm (horizontally only), and its foundation was strong enough to deflect the rupture around itself and survive intact (Wyllie et al., 1977). Indeed the situation not infrequently arises when it is...

00004

Prestressed Concrete Earthquake

Where 00 004 is the curvature at a nominal maximum concrete strain of 0.004, and 0cr is the curvature at first cracking. The ductility or rotation capacity of prestressed concrete is affected by (1) The longitudinal steel content. (2) The transverse steel content. (3) The distribution of longitudinal steel. Each of these variables is discussed below. Longitudinal and transverse steel content From Figure 10.43, it may be seen that ductility decreases markedly with increasing prestressing steel...

845 Eccentrically braced frames

Traditional design of trussed structures lays great importance on keeping the forces in the structure to axial only, avoiding moments by ensuring that the centre-lines of all intersecting members meet at a point, i.e. concentrically (Section 8.4.4). However, starting in the late 1970s, the concept of using deliberately eccentric bracing for earthquake resistance purposes has been found to have certain advantages, so far principally for steel structures, with major structures being designed this...

854 Isolation using flexible piles and energy dissipators

An interesting alternative to the use of lead-rubber bearings is the isolation system used first for Union House (Boardman et al. 1983), a 12-storey office block in Auckland, New Zealand, completed in 1983 (Figure 8.15). As the building required end-bearing piles about 10 m long, the designers took the opportunity of making the piles flexible and separating them from lateral contact with the soft soil layer overlying bedrock by surrounding them with a hollow sleeve, thus creating the...

911 Introduction

As discussed in Chapter 5 the properties and dynamic behaviour of soils and their relationships to structures are complex and involve large uncertainties. In view of the challenges thus imposed on designers of foundations, Pender (1996) proposed three levels of design analysis for foundations, in a review of earthquake resistant design of foundations where design analysis was defined as all the calculation and analysis that is a central part of the design process. He described the three levels...

21 Introduction

An earthquake is a spasm of ground shaking caused by a sudden release of energy in the earth's lithosphere (i.e. the crust plus part of the upper mantle). This energy arises mainly from stresses built up during tectonic processes, which consist of interaction between the crust and the interior of the earth. In some parts of the world, earthquakes are associated with volcanic activity. For example, in Guatemala such earthquakes occur in swarms, with an average duration of three to four months,...

0036

(1) Predominantly cemented limestone. (1) Predominantly cemented limestone. The basis of the microzones was the geology of any deposits overlying bedrock, as mapped in the earlier microzoning study of Suggate and Wood (1979). Their map for Greymouth is reproduced here, slightly annotated, in Figure 6.14. Inangahua and Reefton, are entirely Ground Class C. The Ground Classes AB, C and D conform to the definitions used in the 2002 draft joint Australian New Zealand loadings standard. These...