## Info

Figure 2.6 Comparison of two nonlinear site response models for peak ground acceleration. Both models are from the NGA project with Abrahamson and Silva (2007) and Chiou and Youngs (2006) on the left and right respectively. The Abrahamson and Silva (2007) model shows amplification with respect to the expected value of PGA at a site with VS30 1100 m s while the Chiou and Youngs (2006) model shows the amplification with respect to expected motions on a site with VS30 1130 m s difference in site...

## 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,...

## 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...

## 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...

## 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.

## 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...

## 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...

## 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...

## 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...

## 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...

## 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...

## 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...

## 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...

## 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,...

## 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...

## 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...

## 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...

## 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...