## B

Forced to provide columns with cross-section areas larger than desirable for compatibility with architectural requirements. As noted earlier, EC8 permits the design of structures for non-dissipative behaviour. If this option is taken, then standard concrete design to EC2 should be carried out, the only additional requirement being that reasonably ductile reinforcing steel, lass B or as defined in 2, ust be used. A q factor of up to 1.5 is permitted, this being regarded as effectively an...

## Basic dynamics

His section outlines the key properties of structures that govern their dynamic response, and introduces the main concepts of dynamic behaviour with reference to single-degree-of-freedom (SDOF) systems. 3.2.1 Dynamic properties of structures For linear dyna ic analysis, a structure can be defined by three key properties its stiffness, ass and da ping. For non-linear analysis, esti ates of the yield load and the post-yield behaviour are also required. his section ill concentrate on the linear...

## Check Column Resistances

Design resistances to EC2 Clause 5.4.3.2.1(1) From the Concrete Centre 'How To' Sheet 5 - Columns Using Design Chart for C30 37 concrete and d2 h 0.1 Assume 32 mm diameter main steel d2 45 + 32 2 61 mm d2 h 61 750 0.08 Chart for d2 h 0.1 is most appropriate. Maximum compression N (b*h*Q 4165 *103 750*750*30 0.25 Minimum compression N (b*h*fck) 889 * 103 750*750*30 0.05 Flexure M (b*h2*fJ 1465 * 106 (75 03 * 30) 0.12 Maximum compression A*fyk b*h*fck 0.2 Minimum compression A*fyk b*h*fck 0.3 As...

## Check Shear Approach As For Beams But Without Lateral Load Between Supports

For a conservative design, the column shear could be based upon the flexural capacity at maximum compression calculated above. However, EC8 Equation 5.9 allows the column flexural capacities to be multiplied by the ratio YMRJYMRc on the basis that yielding may develop initially in the beams and hence does not allow the development of the column overstrength moments. VE.d gRd * VMJZMR.XMt.op + bottom) ll For DCM columns, yRJ 1.1 l. 3.5 - 0.75 2.75 m

## Design criteria Capacity design

Capacity design is the basic concept underpinning the EC 8 design philosophy for ductile structures (DCM and DCH). Therefore it is important to fully understand this basic principle in order to place in context the design rules aimed at implementing it. This concept can be exemplified considering the chain, introduced by Paulay (1993) and represented in Figure 5.2, in which link 1 is ductile and all other links are brittle. According to standard design procedures for quasi-static loading...

## Design example composite 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 7.5. The main seismic checks are carried out for a preliminary design according to EN 1998-1. Consideration is only given to the lateral system in the X-direction of the plan, in which resistance is assumed to be provided by moment resisting frames spaced at 4 m. It is also assumed that an independent bracing system is provided in the transverse...

## DrV h

Here d is the design inter-storey drift, V is a reduction factor that takes into account the lower return period of the frequent earthquake and is assumed as 0.5, and h is the storey height. The limit of 1 per cent is applicable to cases where the non-structural components are fixed to the structure in a way that does not interfere with structural deformation. For cases with non-ductile or brittle non-structural elements this limit is reduced to 0.75 per cent and 0.5 per cent, respectively....

## Evk

EsD Young's modulus of soil at depth. These active lengths are somewhat greater than the equivalent lengths that can be determined for piles under static loading. Field studies such as those by Hall (1984) and Makris et al (1996) on instrumented piled structures under significant levels of seismic loading show that the stiffness of the pile group tends to decrease significantly as the number of load cycles increases. )i Constant Stiffness (Typicfb er -cs olidated clay) b) Parabolic Stiffness...

## Fpq

Where f response spectrum frequency considered EsD Young's modulus of soil at depth D L and D length and diameter of pile. Using the appropriate equation, values of F are calculated for discrete frequencies across the frequency range of interest (e.g. 0.5 Hz to 40 Hz). Corresponding values of I are calculated from the following expression (Gazetas, 1984) Iu aF4 + bF3 + cF2 +1.0 (9. 22) The coefficients a, b and c in above equation are given in Table 9.2. he interaction factors produced by this...

## Voe

For dissipative zones of composite beams within moment frames, EN 19981 requires the inclusion of 'seismic bars' in the slab at the beam-to-column connection region. The objective is to incorporate ductile reinforcement detailing to ensure favourable dissipative behaviour in the composite beams. The detailed rules are given in Annex C of EN 1998-1 and include reference to possible mechanisms of force transfer in the beam-to-column connection region of the slab. The provisions are largely based...

## F

Where Fd is the peak force that would be developed in an SDOF system if it responded to the earthquake elastically, and Fy is the yield load of the system. A well-known empirical observation is that, at long periods (> TC), yielding and elastic structures undergo roughly the same peak displacement. It follows that, for these structures, the force reduction is simply equal to the ductility (see Figure 3.11). At shorter periods, the amount of force reduction achieved for a given ductility...

## Sel

Comparing with Equation (3.14) we see that the ratio between spectral displacement and acceleration is times larger for a ductile system than for an elastic one. Thus, the seismic analysis of a ductile system can be performed in exactly the same way as for an elastic system, but with spectral accelerations taken from the design spectrum rather than the elastic spectrum, and with the calculated displacements scaled up by the ductility factor, . For long period structures (T > TC) the result of...

## H

Where v the shear wave velocity at the base of the stratum (depth H). dditional results for an arbitrary increase ith depth stiffness profile are given by Pecker (2005). The stiffness, damping and strength characteristics of the soil column affect the transmission of seismic motions from the bedrock to the ground surface. Various methods are used to assess the seismic motions at foundation level. Direct measurements may be available from the site or another site with similar characteristics. A...

## Non

Figure 9.19 Horizontal and moment loading on pile cap 9.7.8 Pile cap deflection and rotation Design horizontal, shear load VEd 826 kN Lateral load due to the clay layer 1593.4 kN. Note that the lateral load due to the clay layer (kinematic loading) and the design shear load (inertial load) from the superstructure do not occur at the same time. Therefore it is sufficient to consider the largest of these loads in estimating the displacement. However, let us choose to superpose both these loads as...

## I

Finally, the member forces and deformations can be calculated by static analysis. 3.4 Practical seismic analysis to EC8 3.4.1 Ductility and behaviour factor Designing structures to remain elastic in large earthquakes is likely to be uneconomic in most cases, as the force demands will be very large. A more economical design can be achieved by accepting some level of damage short of complete collapse, and making use of the ductility of the structure to reduce the...

## Skz

Figure 6.3 Moments due to gravity and lateral loading components in the seismic situation shear force (VEd) of the column due to seismic combination actions must be less than 50 per cent of the ultimate shear resistance of the section. The beam overstrength parameter (W MplRJMEd) as adopted in EC8 involves an approximation as it does not account accurately for the influence of gravity loads on the behaviour (Elghazouli, 2007). This issue becomes particularly pronounced in gravity-dominated...

## Info

Columns and IPE450 steel profiles (in conjunction with a 150 mm solid slab) for the beams. Composite action is achieved through the incorporation of shear studs in order to attain full interaction according to the provisions of EC4. A preliminary elastic analysis was firstly carried out using the estimated seismic loads for the frame incorporating the initial member sizes. These initial member sizes were, however, found to be inadequate to fulfil both strength and damage limitation...

## Introduction

Earthquake-resistant design can be considered as the art of balancing the seismic capacity of structures with the expected seismic demand to which they may be subjected. In this sense, earthquake-resistant design is the mitigation of seismic risk, which may be defined as the possibility of losses (human, social or economic) due to the effects of future earthquakes. Seismic risk is often considered as the convolution of seismic hazard, exposure and vulnerability. Exposure refers to the people,...

## J

Figure 9.3 Failure of piles in a three-storeyed building in 1995 Kobe earthquake (Tokimatsu et al. 1997) 9.1.2 Lessons learnt from pile foundation failures Pile foundations seem to suffer from earthquake loading for a variety of reasons. A comprehensive list of pile foundations of various structures that have performed poorly was compiled by Bhattacharya, Madabhushi and Bolton (2004). The load bearing soil strata into which the piles are transferring the load ay change their character under...

## J D

Figure 3.16 Isometric view of example building For this preliminary load estimate, neglect weight of frame elements (resulting in same weight mass for steel and concrete frame structures). Assume a. 150 mm concrete floor slabs throughout 0.15 X 24 3.6 kN m2. b. Outer walls - brick block cavity wall, each 100 mm thick, 12 mm plaster on inside face plaster 0.012 X 21 0.25 c. Internal walls - single leaf 100 mm blockwork, plastered both sides d. Ground floor perimeter glazing 0.4 kN m2. e. Floor...

## London And New York

2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN Simultaneously published in the USA and Canada by Spon Press This edition published in the Taylor & Francis e-Library, 2009. To purchase your own copy of this or any of Taylor & Francis or Routledge's collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk. Spon Press is an imprint of the Taylor & Francis Group, an informa business 2009 Spon Press All rights reserved. No part of this book may be reprinted or...

## Material and geometrical restrictions

There are limited material restrictions for DCM structures. In addition to the requirement to use Class B or C reinforcement, as for DCL, only ribbed bars are permitted as longitudinal reinforcement of critical regions and concrete of Class C16 20 or higher must be used. Geometrical constraints are also imposed on primary elements. In order to promote an efficient transfer of moments bettveen columns and beams, and reduce secondary effects, the offset of the beam centre line from the column...

## MEd X kNm

The proportion of live load to be included in the gravity load component in the seismic combination is an area that is open to judgement by the designer based on the use of the building, the ake-up of the live load and the potential consequences of failure. In this case, the minimum vertical load calculated above includes no live load in the gravity component although the lateral loads are based on 30 per cent of the characteristic live load being present. The rationale for this is that whilst...

## MEd x kNm NEd x kN

Figure 7.7 Interaction curve for the first storey composite column Figure 7.7 Interaction curve for the first storey composite column The design checks are performed according to EC4. For brevity, only cross-section checks are presented, but clearly all EC4 resistance checks including those for member stability should also be satisfied. Considering a partially encased HEA500 cross section, for which the axial bending interaction curve is depicted in Figure 7.7, it is evident that the composite...

## Mtop X kNm

He values above are the basic values prior to applying the factor accounting for torsional effects since these are dependent on location. oth the base and design moments need to be increased by the appropriate factor before being used in the design (e.g. for GL 7 and 9, Mbase 19793*1.04 20585 kNm and Mtop 5792*1.04 6024 kNm). a Shear force design diagrams are illustrated in Figure 5.25. The approach to design of the elastic sections at the higher levels is

## Nmax n f B

Where su the undrained shear strength of the soil gs the partial factor for the undrained shear strength. The dimensionless soil inertia F is given by Equation (8.23). a design ground acceleration on type A ground, given by ag yI agR agR reference peak ground acceleration Yj importance factor, depending on the building importance S soil factor. The following constraints apply to the general bearing capacity expression in Equation (8.18). 0 < N < 1, y < 1 (8.24)

## Requirements for critical composite elements Beams acting compositely with slabs

For beams attached with shear connectors to reinforced concrete or composite profiled slabs, a number of requirements are stipulated in Section 7.6.2 of EN 1998-1 in order to ensure satisfactory performance as dissipative composite elements (Concept b). These requirements comprise several criteria including those related to the degree of shear connection, ductility of the cross section and effective width assumed for the slab. Dissipative composite beams may be designed for full or partial...

## S

Location 'Outer' refers to the columns on GL B and E 'Inner' refers to the columns or GL C and D Initially, treat as rectangular - add flange reinforcement later for capacity design. Because of the shape of the bending moment diagram in the short span, it is assumed that no redistribution will take place. M1 (Hogging) 1241 kNm M2 (Sagging) 1189 kNm Design for DCM - bending and shear resistances from EC2 As the example is aimed at demonstrating the application of the seismic engineering...

## S X X cot g

5.9.4.5 Detailing for local ductility eight of the plastic hinge above the base of the all for the purpose of providing confinement reinforcement Design of concrete structures 151 (Equation 5.19 a) hcr < 2.lw 2 X 3.5 7m r w h < 7m evaluation of confinement reinforcement in the boundary elements According to Equation 5.20 an 1 - bt2 (6.b0h0) (Equation 5.16a) All distances (bi, b0, h0, s ) are measured to centrelines of hoops or flexural reinforcement. The values bi are based on the detail of...

## Strength verification

Aving derived the design shear and bending actions in the structural members, the resistances are then calculated according to EC2. If the partial material factors are chosen as discussed in Section 5.2.4 to cater for potential strength degradation, then the design process is simplified. Standard design aids for strength such as Narayanan and Beeby (2005) or guidance available on the Internet (e.g. www.concretecentre.com) can then be used for seismic design. However, EC8 allows National...

## T

For example, the ubiquitous, yet arbitrary (Bommer, 2006a) 475-year return period used in most seismic design codes throughout the world comes from specifying ground motions having a 10 percent chance of being exceeded at least once in any 50-year period. Inserting P 0.1 and T 50 years into Equation (2.5) yields the average annual rate corresponding to this condition, the reciprocal of hich is the return period, that in this case is equal to 475 years. Note that because X is a function of both...

## Vwa Itop f kN

Choose a level at which first curtailment of flexural reinforcement would be appropriate (say at the third-floor level in this instance). Carry out the design for moment and shear as described previously using the values from Figures 5.24 and 5.25 and the axial load appropriate for the level chosen. There is no requirement to detail boundary elements above the height of the critical region other than 2 prescriptions. 5.9.6 Design of frame elements 5.9.6.1 Torsional effects The forces applied to...

## X x x

1 + 0.6 x 1.04 1 + 0.6 x 1.3 56 56 Increase forces output fro the analysis by a factor of 1.3 to account for torsional effects on GL 1 and 15, and by 1.04 on GL 7 and 9. Figure 5.15 Area of influence of the walls Figure 5.15 Area of influence of the walls 142 A. Campbell and M. Lopes 5.9.4.2 Design of the wall base section

## Local ductility provisions

The EC8 design rules take account of the fact that, to achieve the global response reductions consistent ith the q factor chosen, uch greater local ductility has to be available ithin the critical regions of the structure. esign and detailing rules for these critical regions are therefore formulated with the objective of ensuring that Sufficient curvature ductility is provided in critical regions of primary elements. Local buckling of compressed steel within plastic hinge regions is prevented....

## Earthquake parameters and seismicity

An entire book, let alone a chapter, could be dedicated to the issue of seismicity models. Herein, however, a very brief overview, with key references, is presented, ith the ai of introducing definitions for the key parameters and the main concepts behind seismicity models. With the exception of some classes of volcanic seismicity and very deep events, earthquakes are generally produced by sudden rupture of geological faults, releasing elastic strain energy stored in the surrounding crust,...

## Shear Diagram Gl Gl

From the bending moment diagram in Figure 5.24 obtained from analysis the following linear envelope can be established. This diagram must be shifted upwards a distance a1, designated tension shift in EC8 Clause 5.4.2.4(5) , consistent with the strut inclination adopted in the Ultimate Limit State verification for shear. a1 d.cot g9 3150 X 2.5 7875mm 7.875m The design bending moment diagram (MSd) in Figure 5.24(b) is obtained for the design of the all above the plastic hinge.

## P nE

Where EI is the flexural rigidity of the pile and L is the equivalent length of the pile, hich depends on the end conditions. For our case the base of the pile is fixed with sufficient embedment length into the dense sand (5 pile diameters 5 x 0.8 4 m). At the pile cap, the pile head has rotational fixity but not translational fixity. his yields a buckling ode shape that dictates the effective length of the pile to be equivalent to length of the pile. Ignoring the 1 of clay above the...

## Ms Williams

4 Basic seismic design principles for buildings 84 5 Design of concrete structures 106 6 Design of steel structures 175 7 Design of composite steel concrete structures 215 8 Shallow foundations 238 s.p.g. madabhushi, i. thusyanthan, z. lubkowski 9 Pile foundations 279 s.p.g. madabhushi and r. may

## Implementation of EC in Member States

The clauses of Eurocodes are divided into two types, namely Principles, hich are andatory, and Application Rules, hich are acceptable procedures to demonstrate compliance with the Principles. However, unless explicitly specified in the Eurocode, the use of alternative pplication Rules to those given does not allow the design to be made in conformity ith the code. lso, in a given Member State, the basic Eurocode text is accompanied for each of its parts by a National Annex specifying the values...

## Other design considerations

In terms of material properties, apart from the requirements in the concrete and steel parts in EC8 (Sections 5 and 6 of EN 1998-1), additional criteria are specified in Section 7.2 of the composite part (Sections 7 of EN 19981). In dissipative zones, the concrete class should not be less than 20 25 and not higher than C40 50 the upper limit is imposed since the use of typical plastic capacity calculations for composite cross sections may become unreliable when concrete of relatively high...

## Vzx

(a) Fully encased section (b) Infilled section Figure 7.3 Concrete encased open sections and concrete infilled tubular sections As noted above, the detailing rules for critical regions are largely based on those for reinforced concrete columns. The length l of the critical regions at the ttvo ends of columns in moment frames depends on the length and depth of the column as well as on the ductility class (DCM or DCH). The code gives an expression (Equation 7.5 in EN 1998-1) for the minimum...

## Standardisation of seismic design

The first concepts for structural design in seismic areas, the subject of Eurocode 8 (EC8), were developed from experience gained in catastrophes such as the San Francisco earthquake in 1906 and the Messina earthquake in 1908. At the very beginning, in the absence of experimental data, the method used was to design structures to withstand uniform horizontal accelerations of the order of 0.1g. After the Long Beach earthquake in 1933, the experimental data showed that the ground accelerations...

## Groundmotion characterisation and prediction

The crux of specifying earthquake actions for seismic design lies in estimating the ground otions caused by earthquakes. he inertial loads that are ultimately induced in structures are directly related to the motion of the ground upon hich the structure is built. he present section is concerned with introducing the tools developed, and used, by engineering seismologists for the purpose of relating hat occurs at the source of an earthquake to the ground otions that can be expected at any given...

## Dogbone Eccentrically Braced Frames

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...

## Contributors

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...

## Pappin 1991 Design Of Foundation And Soil Structures For Seismic Loading

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...

## 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

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...

## 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...

## References

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.,...

## 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

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...

## 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...

## 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...

## 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...

## 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...

## 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...

## Design and detailing for ductility

Special detailing is required in the 'critical' regions, where plastic hinges are expected to form. These requirements are a mixture of standard prescriptive measures outlining a set of rules to be followed for all structures in a given ductility class and numerically based measures, where the detailing rules are dependent upon the calculated local ductility demand. The latter are typically required at the key locations for assurance of ductile performance such as hinge regions at the base of...

## Campbell and M Lopes

As noted in earlier chapters, EC8 aims to ensure life safety in a large earthquake together with damage limitation following a more frequent event. Whilst the code allows these events to be resisted by either dissipative ductile or non-dissipative essentially elastic behaviour, there is a clear preference for resisting larger events through dissipative behaviour. ence, much of the code is framed with the aim of ensuring stable, reliable dissipative performance in predefined 'critical regions',...

## Overview of this book

Seismic design of structures aims at ensuring, in the event of occurrence of a reference earthquake, the protection of human lives, the Imitation of damage to the structures, and operational continuity of constructions important for civil safety. These goals are linked to seismic actions. Chapter 2 of this book provides a detailed review of methods used in determining seismic hazards and earthquake actions. It covers seismicity and ground-motion models, with specific reference to the...

## Figures

2.1 Schematic overview of seismic hazard analysis 7 2.2 Median predicted values of rupture length and slip 9 2.3 Typical forms of earthquake recurrence relationships 11 2.4 Acceleration, velocity and displacement traces from analogue 2.5 Demonstration of the types of ground-motion parameters that may be calculated from a single record 14 2.6 Comparison of two nonlinear site response models for peak ground acceleration 16 2.7 Explanation of the variance components specified in ground-motion...

## Typical Column Details

Critical Region for full length of short column lc hc lt 3 Critical Region Prescriptive Confinement to clauses 5.4.3.2.2 1 to 4 , 10 and 11 . Critical Region prescriptive Confinement to dauses 5.4.3.2.2 1 to 4 , 10 and 11 . Reduced confinement away from plastic hinge zones. All column splices within this region. Beam Column Joint 'Special' Confinement to clauses 5,4,3,3 fl to 3 Figure 5.8 Typical column details - elevation where wd is volume of confining hoopsf Avolume of concrete core , bQ is...

## Index

Accelerogram 11-12, 36-8, 42, 54, 56, 72 accidental eccentricity 116, 120, 141, 161, 198, 206 active faults 10, 39-40, 244 adjacent structures 98 Alaska earthquake 238, 277 alluvium 56, 246 attenuation 16, 32-3, 40-5 base capacity 282, 284 basin effect 17, 43, 88, 246 Bauschinger effect 188 beam-column joints 113, 123-4, 128, 135-6, 173 see also connections bending links 180 see also long links Bhuj earthquake 280-1, 286-7, 314 bi-directional effects 222 bi-directional resistance 85-6 bond 119,...

## Euler Load For Pile

Euler buckling of equivalent pinned _ Figure 9.5 Buckling mode shape and effective length The concept of slenderness ratio of the pile can also be used to check the pile design for any possible buckling. Slenderness ratio may be defined simply as where r is the minimum radius of gyration of the pile section given by I is the second moment of area about the weakest axis and A is the cross-sectional area of the pile. For a tubular pile the minimum radius of gyration can be estimated as 0.35 times...

## Elastic design response spectra

Most seismic design is based on representing the earthquake actions in the for of an equivalent static force applied to the structure. hese forces are determined from the maximum acceleration response of the structure under the expected earthquake-induced ground shaking, hich is represented by the acceleration response spectrum. The starting point is an elastic response spectrum, which is subsequently reduced by factors that account for the capacity of the structure to dissipate the seismic...

## Time History Record

The peak displacement at resonance is thus very sensitive to damping, and is infinite for the theoretical case of zero damping. For a more realistic damping ratio of 0.05, the displacement of the structure is around ten times the ground displacement. This illustrates the key principles of dynamic response, but it is worth noting here that the dynamic amplifications observed under real earthquake loading are rather lower than those discussed above, both because...

## Seismic displacements

In cases where the transient seismic loadings exceed the available foundation resistance, permanent displacements will occur. Ehe accelerations at which displacement commences are termed threshold accelerations. In many cases the peak earthquake accelerations can exceed the threshold values by a substantial margin with minimal foundation displacement occurring. Ehough EN 1998-5 generally requires that foundations remain elastic, for foundations above the water table, where the soil properties...

## Liquefaction effects on pile foundations

Soil liquefaction is the association of phenomena like piping, boiling, ud volcanoes etc. that lead to severe loss of strength in loose saturated soils. It is well known that loose sandy soils and sandy silts are particularly vulnerable from a liquefaction point of view. In Chapter 8, Sections 8.3.1 to 8.3.3, we have seen how to determine whether a given site is susceptible to liquefaction by using in situ tests such as Standard Penetration Tests SPT or Cone Penetration Tests CPT . EC8 requires...

## Evaluation of the q factor

According to Table 5.1 of EC8 DCM dual system qo 3.0 au a1 The ratio a u a1 depends on the classification of the structure. For multistorey, ulti-bay all-equivalent dual structures, and unless a ore accurate value is obtained by pushover analysis, EC8 allows the assumption that a J a1 1.2. kw 1 28.8 3.5 3 3.06 Therefore k 1 The lateral loads imposed on the structure are based on those derived in Chapter 3 for structures other than moment frames. Thus, the spectral acceleration derived from the...

## Dogbone Connection

Where P and Vtot are the total cumulative gravity load and seismic shear, respectively, at the storey under consideration h is the storey height and d is the design inter-storey drift product of elastic inter-storey drift from analysis and q, i.e. d Xq . Instability is assumed beyond 8 0.3 and is hence considered as an upper limit. If 8 0.1, second-order effects could be ignored, whilst for 0.1 lt 8 0.2, P-D may be approximately accounted for in seismic action effects through the multiplier 1...

## Concentrically braced frames Frame characteristics

Because of their geometry, concentrically braced frames CBFs such as those shown in Figure 6.7, provide truss action with members subjected largely to axial forces in the elastic range. However, during a moderate to severe earthquake, the bracing members and their connections undergo significant inelastic deformations into the post-buckling range, which has led to reported cases of damage in previous earthquakes EERI, 1995 . Figure 6.7 Typical idealised configurations of concentrically braced...

## Detailing

For the critical regions of DCM columns smax min b0 2 175 8dbL EC8 Part 1 Equation 5.18 For columns, take 45 mm cover to the main reinforcement b0 h0 750 - 2 45 10 670 mm centre to centre of link b0 2 335 mm 8 dbL 8 32 256 mm s 175 mm Asw 1.58 175 277 mm2 5 legs of 010 - 392 mm2 Provide five legs of 010 hoops ties at 175 mm spacing within the critical region, 750 mm from the underside of the beam as shown in Figure 5.28. Figure 5.28 Arrangement of column reinforcement Figure 5.28 Arrangement of...

## Pile Foundation Failure

Pile foundations are widely used both onshore and offshore to transfer heavy structural loads to copetent load bearing soil strata or bedrock. eotechnical engineers are called upon to design deep foundations hen the shallo layers of soils beneath the building are either unable to support the loads iposed by the superstructure on the shallo foundations or if the shallow layers may become unstable due to the cyclic shear stresses induced by the earthquake loading. Under such circumstances it is...

## Eccentrically braced frames Frame characteristics

In this type of structural system, as shown in Figure 6.13, the bracing members intersect the girder at an eccentricity 'e', and hence transmit forces by shear and bending. The length of the girder defined by e is termed a 'link beam', which may behave predominantly in either shear or bending. While retaining the advantages of CBFs in terms of drift control, eccentrically braced frames EBFs also represent an ideal configuration for failure mode control. Another important advantage is that by...

## Design example on a pile foundation

In this section e shall outline the design of a pile foundation for a typical column of the building for which the seismic designs were carried out in earlier chapters. f course in reality the design of pile foundations ill be carried out for individual columns with the associated reductions in the pile lengths and or pile diameters to suit the design load on the column. Here we shall only consider one typical column along the D line on the plan of the building. Another premise that is made...

## Liquefaction

8.3.1 Effect of soil liquefaction on structures Liquefaction is a process by which non-cohesive or granular sediments below the water table temporarily lose strength and behave as a viscous liquid rather than a solid hen subjected to strong ground shaking during an earthquake. ypically, saturated, poorly graded, loose, granular deposits ith a lo fines content are ost susceptible to liquefaction. Liquefaction does not occur at random, but is restricted to certain geological and hydrological...

## Eurocode Gusset Plate Connection

AISC 2005 American Institute of Steel Construction Inc., Seismic Provisions for Structural Steel Buildings, AISC, Chicago, IL. ANSI AISC 2005 Prequalified connections for special and intermediate steel moment resisting frames for seismic applications. ANSI AISC 358. AISC, hicago, I. ASCE SEI 2005 ASCE 7-05 - Minimum Design Loads for Buildings and Other Structures, American Society of Civil Engineers Structural Engineering Institute, Reston, VA. Astaneh, A. 1995 Seismic design of bolted steel...

## Comparison of static and dynamic performance requirements of pile foundations

As explained in Section 9.2 the static design of pile must be carried out according to the guidelines provided in EC7 and its provisions. However, it is important to compare the performance requirements of pile foundations under static and dynamic loading. 9.4.1 Kinematic and inertial loading For many classes of structure the predominant static loading on piled foundations is vertical compressive loading. Earthquake loading will impose requirements on the piles to resist significant lateral...

## Ductility classes and rules for cross sections

To achieve some consistency with other parts of the code, the most recent version of EC8 explicitly addresses three ductility classes namely DCL, DCM and DCH referring to low, medium and high dissipative structural behaviour, respectively. For DCL, global elastic analysis and the resistance of the members and connections may be evaluated according to EC3 without any additional requirements. The recommended reference q factor for DCL is 1.5-2.0. For buildings that are not seismically isolated or...

## Reinforcement In Beams Parts

Along the entire length of the bea and not just in the critical regions . In this expression, fctm is the mean value of concrete tensile strength as defined in Table 3.1 of EC2 and fyk is the characteristic yield strength of the reinforcement. To ensure that yielding of the flexural reinforcement occurs prior to crushing of the compression block, the maximum amount of tension steel provided, pmax, is limited to Here, tsyd is the design value of reinforcement strain at yield, p' is the...

## Design example on a shallow foundation pad foundation Sites

There are four sites A, B, C and D that are available for construction of the hotel as stated in Chapter 4 Section 4.8 . Figure 8.12 Assessment of volumetric strain Tokimatsu amp Seed, 1987 Figure 8.12 Assessment of volumetric strain Tokimatsu amp Seed, 1987 The design ground acceleration is taken as agR 0.3g. The building importance factor for the hotel is taken as y 7 1 in this example. Preliminary site investigation was carried out at all the sites. Borehole data and SPT and field vane shear...

## Pile foundation design under static loading

He static design of the pile foundations has to be carried out in accordance with EC7. A procedure is outlined below for cohesionless soils. A similar approach can be used for cohesive soils ith suitable odification. The pile capacity can be determined as a combination of the base capacity and the shaft capacity he base capacity depends on the bearing capacity of the soil at the pile tip level. It can be calculated using Figure 9.4 Bearing capacity factor N for deep foundations Figure 9.4...

## Manual For Seismic Design Afps

Figure 4.8 Structural layout taken for regularity checks The floor slabs in the tower are rectangular, without branches, and have an aspect ratio in the tower see 4 below of 56 m 20 m 2.8, which is relatively compact. Given the uniform distribution of mass and lateral load resisting elements i.e. the frames and shear walls in the long direction, a continuous concrete solid slab or topping slab over precast elements of at least 70 mm would not be expected to give rise to uneven load...

## Moment Resisting Frame

Investigated by several researchers e.g. Lay and Galambos, 1967 Kato and Akiyama, 1982 Kato, 1989 . In subsequent sections, the behaviour of the three ain configurations of steel frame structure, namely moment resisting, concentrically and eccentrically braced frames, is discussed. Whereas moment-frames exhibit relatively ductile behaviour under earthquake loading, their lo lateral stiffness may, in some situations, result in high storey drifts, thus leading to unacceptable damage to...