F Hql
ure 3.11 Equivalence of ductility and behaviour factor with equal elastic and inelastic displacements When designing structures taking account of non-linear seismic response, a variety of analysis options are available. he siplest and ost idely used approach is to use the linear analysis ethods set out above, but ith the design forces reduced on the basis of a single, global behaviour factor, q. EC8 gives recommended values of q for common structural forms. This approach is ost suitable for...
Info Wem
Figure 2.5 Demonstration of the types of ground-motion parameters that may be calculated from a single record. The record in this case is the 020 component recorded during the 1994 Northridge earthquake at the Saturn St. station in Los Angeles. The three panels on the left show the acceleration, velocity, and displacement time-series as well as the peak and root-mean-square rms values. The panels on the right show, from top to bottom, a Husid plot of the build-up of Arias intensity as well as...
L
where a is the ratio of the absolute value of the smaller-to-larger bending moments at the ttvo ends of the link. If the applied axial force exceeds 15 per cent of the plastic axial capacity, reduced expressions for the moment and shear plastic capacities are provided in EC 8 to account for the corresponding reductions in their values. EC8 also provides limits on the rotation '8p' in accordance with the expected rotation capacity. This is given as 0.08 radians for short links and 0.02 radians...
Info Jzn
More comprehensive and complex checks for the shear resistance and confinement requirements at beam column joints are introduced. uch ore stringent checks on the resistance to shear by diagonal tension and diagonal compression are introduced, namely the limitation of the strut inclination to 45 and the reduction of the resistance to diagonal compression of the web in the critical region to 40 per cent of the resistance outside the critical region. different verification is also introduced of...
Info Fgv
Figure 2.17 Comparison of 5 -damped displacement response spectra for a stiff soil site at 10 km from earthquakes of different magnitudes from Akkar and Bommer 2007b with the EC8 Type 1 spectra for the same conditions, anchored to the PGA value predicted by the equation presented in the same study Figure 2.17 Comparison of 5 -damped displacement response spectra for a stiff soil site at 10 km from earthquakes of different magnitudes from Akkar and Bommer 2007b with the EC8 Type 1 spectra for...
Contributors
P. Bisch is a specialist in structural analysis and presently Professor at the Ecole Nationale des Ponts et Chauss es ENPC in Paris. In 1976, he joined Sechaud amp Metz S amp M , Consulting Engineers, as Technical Director and is now Scientific Director with the IOSIS group, to which S amp M belongs. He was formerly President of the European Association for Earthquake Engineering and also Vice-President of CEN TC250 SC8 on EC8, for which he is the current French National Technical Contact. He...
References Puo
Ambraseys, N.N. and Menu, J.M. 1988 Earthquake-induced ground displacements. Earthquake Engineering amp Structural Dynamics, 16, 985-1006. Auvinet, G., Pecker, A. and Salenjon, J. 1996 Seismic bearing capacity of shallow foundations in Mexico City during the 1985 Michoacan earthquake. Proceedings of the 11th World Conference on Earthquake Engineering, Acapulco. Bird, J.F. and Bommer, J.J. 2004 Earthquake losses due to ground failure. Engineering Geology, 75 2 , 147-179. Borcherdt, R. and...
a a a
an 1 - 1 b 2 6b0h0 EC8 Part 1 Equation 5.16a as 1 - s 2b0 1 - s 2h0 EC8 Part 1 Equation 5.17a Since the normalised axial compression is greatest at the base of the column, consider the detailing of this region to check the feasibility of the design. All main column bars are equally spaced b 660 - 32 4 157 mm an 1 - 16 1572 6 670 670 0.85 as 1 - s 1340 1-s 1340 For s 100 mm, a 0.85 For s 125 mm, a 0.82 2 q - 1 2 3.6 - 1 6.2 esyd 434.8 200E3 0.0022 vd 0.53 30j vfsy4 bc b0 - 0.035 30 6.2 0.53...
Info Cqb
Medium-dense to dense sand 1.00 where NEd, VEd and MEd are the design action effects at the foundation level, and the rest of the numerical parameters in Equations 8.18 to 8.21 depend on the type of soil and are given in Tables 8.5 and 8.6.
Info Gtg
Figure 2.16 Amplification factors for 1.0-second spectral acceleration for different site shear-wave velocity values relative to rock motions for Boore et al. 1997 , rock has been assigned a shear-wave velocity of 800 m s A number of interesting observations can be made regarding the curves in Figure 2.16, the first being the wide range of proposed amplification factors for different sites, especially those overlain by soft soil layers. The second observation that can be made is that...
Info Cyy
Figure 2.10 Example of a suite of PGA hazard curves obtained from a logic tree for a fictitious site Figure 2.10 Example of a suite of PGA hazard curves obtained from a logic tree for a fictitious site model selection, model compatibility and the overall sensitivity of PSHA to logic-tree branches for ground-motion models have all been addressed Scherbaum et al., 2004a, 2004b Sabetta et al., 2005 Bommer et al., 2005 Scherbaum et al., 2005, Beyer and Bommer, 2006 Cotton et al., 2006 as have...
Shaft Friction
We can ignore the 1 m of clay layer just below the pile cap in estimating the shaft capacity conservative assumption Assume the following For driven piles K lt 1, choose K 1. For the loose sand layer around the shaft, 30 . s e are using driven, sooth, steel tubular piles 3 3 X 30 20 Therefore, at 12.53 m elevation Ts 1 x 40 X tan 20 14.55 15kPa At -1.47 m elevation 15 m long pile T s 1x180 X tan 20 65.5 66kPa qs 2nr xfgL xs Q 2n x 0.4 x 15 66 x15 1527kN 2 x1000 The applied design load for...
Structural types and behaviour factors 1
Ehe same upper limits of the reference behaviour factors specified for steel framed structures Section 6 of EN 1998-1 are also employed in Section 7 of EN 1998-1 for composite structures. Ehis applies to composite moment resisting frames, composite concentrically braced frames and composite eccentrically braced frames. However, whilst in composite moment frames the dissipative beam and or column zones may be steel or composite, the dissipative zones in braced frames are in most cases only...
Torsional effects
A simplified approach towards catering for the increase in seismic forces due to accidental eccentricity in regular structures is given in Clause 4.3.3.2.4 of EC8 Part 1. Loads on each frame are multiplied by a factor, 5, equal to 1 0.6 x L where x is the distance of the frame from the centre of mass and L is the distance bettveen the two outermost load resisting elements. Hence, for a building where the mass is uniformly distributed, the forces and moments on the outermost frames are increased...
Aaaa
where A is the area of the cross section of the tension diagonal and a is the slope of the diagonal to the horizontal. In V-bracing, both tension and compression bracing members are needed to resist horizontal seismic forces effectively, hence both should be included in the elastic analysis of the frame. Also, the beams should be designed for gravity loading without considering the intermediate support of the diagonals, as ell as account for the possibility of an unbalanced vertical action...
Acceleration timehistories
Although seismic design invariably begins with methods of analysis in which the earthquake actions are represented in the form of response spectra, some situations require fully dynamic analyses to be performed and in these cases the earthquake actions ust be represented in the for of acceleration time-histories. Such situations include the design of safety-critical structures, highly irregular buildings, base-isolated structures, and structures designed for a high degree of ductility. For such...
B N
where av vertical ground acceleration, given by av 0.5 ag S N bearing capacity factor, given by Equation 8.26 where f', design shearing resistance angle given by Equation 8.27 where f' is the shearing resistance_angle. The dimensionless soil inertia F is given by Equation 8.28 The following constraints apply to the general bearing capacity expression in Equation 8.18 where k a coefficient fr m Eable 8.5. Ehe previous formulation has been recently extended to circular foundations on homogeneous...
End Bearing
onsider the end bearing of a pile. End bearing of pile ay be calculated as where Ab base area of shaft, assuming fully plugged base. The friction angle for dense sand 36 . The bearing capacity factor, Nq, for a deep foundation can be obtained using the chart given by Berezantzev et al 1961 shown earlier in Figure 9.4. Reading the value of N from this figure for the friction angle of 36o, we get N 65 Assume that the pile starts from 1 m below ground level to allow for pile cap of 1 m thickness....
Siting requirements General
The primary cause of building damage has been identified as ground shaking however, in most earthquakes the overall damage to buildings is caused by more than one hazard. The principal secondary cause of building damage is ground failure, which can be divided into five elements, namely fault rupture, topographic amplification, slope instability, liquefaction and shakedown settlement Bird and Bommer, 2004 . Section 4 of EN 1998-5 2004 requires that these earthquake phenomena are identified and...
Info Ovk
h0 7 X 80 5x85 ---1---1---1-- 1024mm In the evaluation of the dimension of the boundary elements it was assumed the diameter of the stirrups and hoops is 9 10mm. The proposed detail of the boundary elements meets EC8 and EC2 requirements. According to Clause 5.3.4.3.2 9 of EC8, it is only necessary that 'every other longitudinal bar is engaged by a hoop or cross-tie' and according to Clause 5.4.3.2.2 11 'the distance bettveen consecutive longitudinal bars engaged by hoops and cross ties does...
References Hyo
Berezantsev, VG. 1961 Load-bearing capacity and deformation of piled foundations, Proc. IV International Conference on Soil Mechanics, Paris, 2 11-12. Bhattacharya, S. Madabhushi, S.PG. and Bolton, M.D. 2003 An alternative mechanism of pile failure during seismic liquefaction, Geotechnique, 54 3 , 203213. hattacharya, S., olton, and adabhushi, S.P 2005a reconsideration of the safety of piled bridge foundations in liquefiable soils, Soils and Foundations, 45 4 , 13-26. Bhattacharya, S.,...
References 1
Fardis M N, Carvalho E, Elnashai A, Faccioli E, Pinto P and Plumier A 2005 Designers' Guide to EN 1998-1 and EN 1998-5 Eurocode 8 Design of structures for earthquake resistance. General rules, seismic actions, design rules for buildings, foundations and retaining structures. Thomas Telford, London. Institution of Structural Engineers SECED AFPS 2009 Manual for the Seismic Design of Steel and Concrete Buildings to Eurocode 8. In preparation. Narayanan R S and Beeby A 2005 Designers' Guide to EN...
Info Tfp
Figure 5.21 Detail of boundary element with overlapping hoops an l- 2 x 7 x 802 3 x 762 2 x 5 x 852 6 x 270 xl024 0.89 This represents an increase of around 8 per cent in the efficiency of confinement. he layout of the inner stirrups is also less efficient than it could be. Figure 5.20 shows that the concrete between the inner hoops is less confined than the concrete ithin these hoops the expansion of the concrete ithin the inner hoops is restricted in the direction of the largest dimension of...
Design example moment frame Introduction
The same eight-storey building considered in previous chapters is utilised in this example. The layout of the structure is reproduced in Figure 6.17. The main seismic design checks are carried out for a preliminary design according to EN 1998-1. For the purpose of illustrating the main seismic checks in a simple manner, consideration is only given to the lateral system in the X-direction of the plan, in which resistance is assumed to be provided by MRFs spaced at 4 m. It is also assumed that an...
Design For Dcm And Dch
Clearly the dual structure gives rise to significantly larger forces because its lower period puts it closer to the peak of the response spectrum . However, it also provides a more efficient lateral load-resisting system, so it will not necessarily be uneconomic. Steel braced frames have not been considered explicitly here. They would give rise to similar design forces to the dual system, since EC8 recommends the use of the same Ct value in the period calculation, and allows use of a slightly...
Design of structural systems Composite moment frames
Composite moment frames, consisting of steel or composite columns and steel or encased filled beams acting compositely with reinforced concrete or composite slabs, can offer several behavioural and practical advantages over bare steel and other alternatives. Ehe seismic behaviour of composite moment frames has been examined experimentally and analytically by several researchers e.g. Plumier et al, 1998 Leon, 1998 Leon et al, 1998 Hajjar et al, 1998 Ehermou et al, 2004 Spacone and El-Eawil, 2004...
Design Wall With Ec2 Ec8
V7777777777777777777, lt LaN gt Cwall Ccofumn Srtall gt gt 6column -',,J gt gt Ecoluoin Figure 5.11 Unavoidability of wall hinging 5.7.2 Calculation of action effects Figure 5.3 highlights that for the best seismic performance the walls must act as vertical cantilevers and only be allowed to develop a single plastic hinge at the base. The formation of this hinge is practically unavoidable, which can be explained as follows both walls and frames have to withstand similar displacements at floor...
Check for liquefaction
Nspt from a field SPT test are to be normalised as given below to obtain N1 60 . For the present site, this has already been done and values of Nt 60 are given. ER the ratio of the actual impact energy to the theoretical free-fall energy. In Europe a value of ER 70 per cent is commonly used. However, it is recommended that as much as possible, measurements of ER should be made at the start of the site investigation as the values for ER vary significantly from one equipment to another and even...
Design of the wall above the plastic hinge
he design of the all above the plastic hinge at the base is different fro the design of the plastic hinge in to ain features 1 It is based on the provisions of E2, since all these zones are supposed to remain in the elastic range throughout the seismic action. There is no need to provide confinement reinforcement. 2 In order to ensure that the wall remains elastic above the base hinge considering the uncertainties in the structure dynamic behaviour, the design bending moments and shear forces...
Seismic Load Combinations Eurocode
The radius of gyration, l, is the square root of the ratio of the polar moment of inertia to the mass, the polar moment of inertia being calculated about the centre of mass. For a rectangular building of side lengths l and b, and a uniform mass distribution, Equation 4.3 applies. The requirement for torsional radius r to exceed 3.33 times the mass-stiffness eccentricity e item 5 on the list at the beginning of this section relates the torsional resistance to the driving lateral-torsional...
Capacity Design
8y oul 2G6y S By 8 Sy 6 Figure 5.2 Ductility of chain with brittle and ductile links 8y oul 2G6y S By 8 Sy 6 Figure 5.2 Ductility of chain with brittle and ductile links According to capacity design principles, to maximise the ductility of the chain, some links have to be chosen to have ductile behaviour and be designed with that purpose. The rest of the structure must be designed with excess strength in order to remain elastic during the plastic deformations of the ductile links. For this...
Tables
1.1 Parts of Eurocode 8 3 2.1 Proper partitioning of the total uncertainty associated with ground-motion modelling into distinct modelling 25 3.1 Dead load calculation 75 3.2 Imposed load calculation 76 3.3 Seismic mass calculation 76 3.4 Lateral load distribution using linear mode shape approximation 79 3.5 Total lateral forces for different frame types 81 4.1 Importance classes 97 5.1 Basic value of the behaviour factor, q0, for systems regular in elevation 110 5.2 Horizontal displacements...
Strength verification 1
Just as for the frames, both flexural and shear verifications for walls of DCM structures follow standard EC2 procedures. Flexural reinforcement should be concentrated at the extremities of the section, in the zones furthest aay fro the neutral axis. his is also the ost efficient distribution of the flexural reinforcement in terms of curvature ductility. The minimum longitudinal reinforcement ratio in the boundary elements is 0.005. In three-dimensional elements, resulting from the intersection...
m x
v 5956 10- 0.243 Clause 5.4.3.4.1 2 bhfcd 350 x 3500 x 20 vm x lt 0.4 the design axial force does not exceed the maximum limit for structures. Um x gt 0-2 it is necessary to design the boundary elements explicitly for ductility according to EC8 Clause 5.4.3.4.2 12 . Situation with N design using Concrete Centre charts from www. concretecentre.com . Note these are based on characteristic concrete strength f k rather than design strength fcd.
Conclusions and recommendations
For most engineering projects in seismic zones, the earthquake loading can be represented by an acceleration response spectrum, modified to account for inelastic deformation of the structure. The elastic design spectrum will most frequently be obtained through probabilistic seismic hazard analysis, which provides the most rational framework for handling the large uncertainties associated with the models for seismicity and ground-motion prediction. Most seismic design codes present zonation maps...
Material and construction considerations
In addition to conforming to the requirements of EN 1993-1 2005, EC3 , EC8 incorporates specific rules dealing with the use of a realistic value of material strength in dissipative zones. In this respect, according to Section 6.2 of EN 1998-1, the design should conform to one of the following conditions The actual maximum yield strength f of the steel of the dissipative zones satisfies the relationship f lt 1.1 g f, where f is the nominal yield strength and the recommended value of g is 1.25....
Structural types
EC8 Part 1 classifies concrete buildings into the following structural types dual system, which may be either frame or wall equivalent system of large, lightly reinforced walls torsionally flexible syste. Apart from torsionally flexible systems, buildings may be classified as different systems in the two orthogonal directions. Frame systems are defined as those systems where moment frames carry both vertical and lateral loads and provide resistance to 65 per cent or more of the total base...
Contents of EC
EC8 comprises six parts relating to different types of structures Table 1.1 . Parts 1 and 5 form the basis for the seismic design of new buildings and their foundations their rules are aimed both at protecting human life and also limiting economic loss. It is interesting to note that EC 8 Part 1 also provides design rules for base isolated structures. Particularly because of its overlap ith other Eurocodes and the cross-referencing that this implies, EC 8 presents some difficulties at first...
E Booth and Z Lubkowski
Fundamental decisions taken at the initial stages of planning a building structure usually play a crucial role in determining how successfully the finished building achieves its performance objectives in an earthquake. This chapter describes how EC8 sets out to guide these decisions, with respect to siting considerations, foundation design and choice of superstructure. 4.2 Fundamental principles 4.2.1 Introduction In EC8, the fundamental requirements for seismic performance are set out in...
Seismic hazard analysis
The primary objective of engineering seismology is to enable seismic hazard analyses to be conducted. he to previous sections have provided ost of the essential background required to understand seismic hazard analysis at its most basic level. As will soon be demonstrated, the mechanics of hazard analysis are relatively straightforward. However, a thorough understanding of the concepts laid out in the sections thus far, as ell as any others, is a prerequisite for conducting a high-quality...
Structural types and behaviour factors
There are essentially three main structural steel frame systems used to resist horizontal seismic actions, namely moment resisting, concentrically braced and eccentrically braced frames. Other systems such as hybrid and dual configurations can be used and are referred to in EC8, but are not dealt with in detail herein. It should also be noted that other configurations such as those incorporating buckling restrained braces or special plate shear walls, which are covered in the most recent North...
Dcm Aij
apply in the case of composite members, as discussed in subsequent parts of this chapter. If dissipative steel zones are ensured, the cross-section rules described in the previous chapter and in Section 6 of EN 1998-1 should be applied. For dissipative composite sections, the beneficial presence of the concrete parts in delaying local buckling of the steel components is accounted for by relaxing the width-to-thickness ratio as indicated in Table 7.2. In Table 7.2 which is adapted from Table 7.3...
AY Elghazouli and JM Castro
W mm NplM, NEd 1983 1957 1.01 The design combination is therefore The design forces for a critical beam Element 42 in Figure 6.21 and a critical column Element 10 in Figure 6.21 are presented in Tables 6.12 and 6.13, respectively, for illustration. Based on these values, the seismic demands at mid-span of the beam are NEd -3.6 1.39X -908.1 -1266 kN The combination of MEd and NEd given above should be used to perform all resistance checks for the member under consideration, including those for...
Eurocode 2 Spacing Of Hoops
if the diameter of the inner hoops is reduced to 9 8mm V 2318 X 78.5 3094 X 50 2693304mm2 m dopt exterior hoops stirrups fro one edge of the all section to the other 2 legs 010 at 125 mm spacing. Adopt inner hoops according to the detail of the boundary elements 08 at 12 5 spacing. 5.9.4.6 Improvements to the detail of the boundary elements Designers will generally have several options for the design of walls' boundary elements. in this section some possible improvements of the detail of the...
Where Is The Damping In The Design Spectrum Ec8
Figure 3.9 EC8 5 damped, elastic spectra, a type 1, b type 2 Figure 3.9 EC8 5 damped, elastic spectra, a type 1, b type 2 denoted by Se, normalised by a , the design peak ground acceleration on type A ground. The spectra are plotted for an assumed structural damping ratio of 5 per cent. See EC8 Cl. 3.2.2.2 for mathematical definitions of these curves and EC8 Table 3.1 for fuller descriptions of ground types A-E. As with the harmonic load case, there are three regimes of response. Very stiff,...
Srn K [m Zffli
With the impedance functions defined in the above equations, any appropriate static expression for single pile or pile group loading response can be used for the dynamic loading case, substituting the complex impedance terms for their static counterparts. Numerical studies undertaken by Gazetas 1984 show that k w is approximately unity for most practical values of pile - soil stiffness ratio over the frequencies of interest and for the horizontal, rocking and vertical modes. Hence the dynamic...
Critical Regions 1
These are the regions adjacent to both end sections of all primary seismic columns. The length of the critical region where special detailing is required is the largest of the following where hc is the largest cross-section dimension of the column and ld is the clear length of the column. The whole length of the column between floors is considered a critical region for structures ith asonry infills if it is a ground floor column if the height of adjacent infills is less than the clear height of...
L M
Similarly for displacements, by analogy with Equation 3.14 M,. d '4k y- max -S . ' r 3.28 To find the horizontal force on mass j in mode i we simply multiply the acceleration by the mass and the total horizontal force on the structure usually called the base shear in mode i is found by summing all the storey forces to give The ratio L 2 M. is known as the effective modal mass. It can be thought of as the amount of mass participating in the structural response in a particular ode. If e su this...
Concrete design example wallequivalent dual structure Introduction
The concrete design example is based on a dual frame solution for the eight-storey hotel introduced in earlier chapters. For clarity, the example only considers the critical transverse direction with primary frames at 8 m spacing. The frames on GLs 1, 7, 9 and 15 incorporate structural walls whereas those on GLs 3, 5, 11 and 13 are moment frames. In a typical frame, transverse beams support masonry cross-walls bettveen GLs B and C, and D and E, primary beams fulfilling this function on odd...
Info Rna
Figure 8.6 Determination of liquefaction potential Figure 8.6 Determination of liquefaction potential Note that EC8 Part 5 Clause 5.1.4 11 requires liquefaction factor of safety check. Normalised data is put into Figure B.1 in Annex B of EC 8 Part 5. From the plot in Figure 8.6 we can determine that liquefaction is possible in the loose sand layer. Conclusion the loose sand layer from elevation 12.53 to 2.53 i.e. 10 m of sand layer is susceptible to liquefaction. 8.4 Shallow foundations 8.4.1...