Avigdor Rutenberg

Technion – Israel Institute of Technology | technion · Faculty of Civil and Environmental Engineering

Many existing old buildings constructed in Israel several decades ago are still in service and are likely to remain so for a relatively long time. Such buildings were commonly built using poor materials and construction practices. They include exterior walls, as well as interior partitions, which form part of the vertical gravity structural system....

This paper describes an experimental study to evaluate the shear capacity of small to medium height old buildings constructed in Israel more than 50 years ago with poor materials and construction practices resulting in low performance concrete (LPC), also known as plum concrete. Such LPC is characterized by its low compressive strength and in many...

Strengthening of existing buildings, especially those constructed several decades ago, is crucial. In the Mediterranean region (and especially in Israel), many such old buildings were built using poor materials and construction practices. They include exterior walls, and in many cases also interior partitions, which are part of the vertical gravity...

An approximate method is proposed for the dynamic analysis of torsionally coupled tall building structures by utilizing the properties of their uncoupled counterparts. An exact solution is first given for the particular case in which the lateral and torsional stiffness matrices are uncoupled by same transformation. The method is then applied to a w...

SUMMARY Mid-rise to high-rise buildings in seismic areas are often braced by slender reinforced concrete (RC) walls, which are interconnected by RC floor diaphragms. In design, it is typically assumed that the lateral forces are distributed in proportion to the wall's elastic stiffness. Pushover analyses of systems comprising walls of different len...

Effect of higher vibration modes on the seismic shear demand of reinforced concrete cantilever walls has been studied since the 1970’s. The shear amplification becomes more important with increasing fundamental period (tall buildings) and increasing ductility demand (R or q factors). Yet, studying the relevant recommendations of structural engineer...

This paper presents results of the first stage of an experimental research program on the pounding response of adjacent concrete structures during earthquake. It shows experimental results for longitudinal impact of concrete rods. The impact of concrete to concrete surfaces of the rods was studied and the coefficient of restitution was experimental...

A simple structural model is proposed to evaluate the axial force acting on tie beams interconnecting spread footings or pile caps due to differential ground motion estimated on the basis of the travelling wave assumption. The approach is intended to supplement the "ten percent rule" or similar multipliers specified by seismic codes as design axial...

Site-specific seismic response factors for low-period building structures are presented as an alternative to the recently proposed foundation factor F* for inclusion in the seismic provision of the National Building Code of Canada. These factors are not explicit functions of the site vibration period, and, therefore, are more suitable for the desig...

Recent trends in the specifications of earthquake design forces are moving away from spectral amplification of ground motion towards direct evaluation of spectral values. Also, the 1988 Saguenay earthquake produced strong evidence for the need to modify the present provisions for low period structures in eastern North America. A new database consis...

Several approximate formulae for the determination of natural frequencies of interconnected walls and frames with uniform mass and stiffness throughout their height are compared and the range of their applicability discussed. It is found that none of the approximations give high accuracy for the entire range of the stiffness parameter αH encountere...

Experimental results are presented on three externally reinforced concrete block walls subjected to in-plane cyclic lateral loading, the walls being confined by flexible steel frames. All three specimens were of similar construction, the varying parameter being the steel reinforcement ratio in the outer skins. The load deflection curves, stiffness...

The primary purpose of this paper is to discuss the separation of travelling wave effects from the mass center to resistance center eccentricity effects, and to propose means by which the torsional spectrum (or a torsional seismic factor) could be incorporated in the seismic provisions of the National Building Code of Canada. The paper begins the t...

The seismic shear provisions of EC8 for ductile reinforced concrete walls, serving as the lateral load resisting system in multistorey building structures are re-examined. Two aspects are considered (1) single walls, or a system comprising a number of equal-length walls, (2) a resisting system comprising walls of different lengths. It is demonstrat...

This paper uses the equivalent linearization approach to derive the approximate harmonic equivalent stiffness and damping for bilinear systems in the context of earthquake resistant design. Whereas the resulting stiffness is identical to that in published works, the damping herein depends on the harmonic output frequency as well. This additional de...

This paper is concerned with the design of friction dampers designed to slip at a predetermined level and dissipate a substantial portion of the seismic energy, leaving the structure practically intact without its members having to yield or buckle. They are appropriate for use in seismic design of new buildings and in retrofitting existing structur...

This report presents a study of irregular structures near collapse, aimed to understand better the influence of irregularities and adequacy of simplified techniques of analyses to real behavior of such structures. Experience shows that buildings with irregularities are prone to severe damage as demonstrated in many earthquake occurrences. An experi...

The distribution of seismic base shear demand among ductile flexural cantilever walls, comprising the lateral load resisting system of a multistorey building, is studied. It is shown that the base shear force demand depends on the sequence of hinge formation at the wall bases, and this in turn depends on the relative wall lengths. Hence, the routin...

The seismic behaviour of regular multistorey structures supported laterally by a number of reinforced concrete cantilever walls with markedly different lengths is addressed. It is shown that the shear force distribution among the walls is strongly affected by the different yield displacement levels of the walls. The share of the shear force carried...

A simplified analysis of local site amplification effects on the seismic response of multi-support structures is presented. The site effects are modeled by considering reflections and transmission of vertically propagating shear waves from bedrock to the surface through a soil layer. A random vibration-based response spectrum of a simple oscillator...

This paper is concerned with the seismic design of steel frames using friction damped slotted bolted connections (SBCs) in the diagonal braces as a means for passive control. A dynamic model that uses bilinear hysteretic behavior for the damper describes the response of a single degree of freedom (SDOF) steel frame and constitutes the basis for the...

This paper is concerned with the design of steel frames using friction damped slotted bolted connections (SBCs) in the diagonal braces. A dynamic model is developed to describe the behaviour of a single-degree-of-freedom (SDOF) steel frame that uses bilinear hysteretic behaviour for the damper. This model is generalized to MDOF systems. A novel alg...

The paper consists of two parts. The first part describes the results of a limited survey of damage to elevator systems during the 1995 Gulf of Eilat earthquake. The second part summarizes an analytical study on the seismic response of counterweight guide rails. The analytical part utilizes a mathematical model that the authors developed earlier, s...

This paper evaluates the stability bounds of the force reduction factor R of unidirectionally loaded UBC designed asymmetric one-storey systems having different mass and stiffness distributions. It is shown that whereas the instability effects due to torsional response are neutralized by the asymmetry-related over strength, instability bounds may s...

The paper presents a numerical sensitivity study of the local site effects on structural response. Following a recently developed model of spatial coherency and a concept of a simple site coefficient the local site effects are modelled as filtrations of excitation processes with a frequency shift. An analysis of a bridge response with supports foun...

The seismic response of single storey asymmetric structures modelled as two-degree-of-freedom elastic-perfectly plastic oscillators and designed using the design eccentricity formula of the present Uniform Building Code (UBC) torsional provisions, which first appeared in the 1988 edition, is compared with designs based on the earlier UBC 1979. Chan...

This paper studies the seismic response of structure-elevator systems. Dynamic models are developed to represent the structure and elevator counterweight subsystems, with nonlinear contact elements between the counterweight and the guide rails. The computational output is given in terms of maximum rail stresses, relative elastic deflections, and in...

Results of a parameter study on eccentric pounding of two symmetric single storey systems under seismic excitation are presented. Linear behaviour is assumed, and pounding effect is considered using the restitution coefficient approach. The effect of impact eccentricity is studied on two sets of symmetric models symmetrically and asymmetrically ali...

The construction of health-care facilities is similar to that of other buildings. Yet the need to function immediately after an earthquake, the helplessness of the many patients and the high and continuous occupancy of these buildings, require that special attention be paid to their seismic performance. Here the lessons from the California experien...

The examined model consists of two substructures linked by a right angle rigid line joint. One element is a wall loaded externally along its upper edge by an uneven vertical load. The other element, defined as a plate, is not loaded. Stresses and displacements in the vicinity of the joint are analysed, considering the lateral distribution which lea...

Several analytical and experimental studies have been recently conducted on the behavior of cross-bracing systems subjected to out-of-plane buckling. Semirigid connections, however, were not considered or modeled. This paper derives and solves for the exact expressions for evaluating the effective length factors of semirigidly connected cross braci...

In recent years, several analytical studies have been conducted on the behavior of cross-bracing members subjected to out-of-plane buckling. Most of these studies do not consider boundary conditions such as the relative stiffness of the end connections and adjoining members and eccentricity in loading. In this paper closed-form relationships are ob...

The effect of setbacks on the lateral load response of symmetric and asymmetric high-rise shear wall buildings is investigated. It is shown that the shear deformation of walls and in-plane flexibility of floor slabs appreciably affect the distribution of lateral loads among the walls in the vicinity of the setback. On the whole, these effects are b...

A parametric study of the inelastic earthquake response of single storey asymmetric structures is presented. The aim is to compare the behaviour of structures designed by the static seismic provisions of the ATC3 Code with those of the 1985 National Building Code of Canada (NBCC). Three different configurations of the resisting system were analysed...

The effect of in-plane roof bracing rigidity on the stability of columns in one-story industrial buildings with light roofing is investigated. To simplify the analysis, expressions for the equivalent constants of the springs laterally supporting the columns at roof level are derived for common types of bracing, including roof metal decks. Effective...

In an earlier paper the results of a parametric study of the seismic response of medium to long period asymmetric structures were reported and design formulae were proposed. Here the corresponding results for low period structures are presented with applicable modifications to the proposed design formulae.

A simple approximate lower bound formula is proposed for the gravity buckling loads of coupled shear-wall structures using continuous medium assumptions. The deflected shape of the system is decomposed into those of flexural and shear-flexure cantilevers. For the latter, an accurate approximate buckling load formula is also presented. Inserting the...

The seismic analysis of structures for travelling wave effects usually requires multiple support excitation procedures which are not well established for piping systems in nuclear power plants, arch dams, pipelines and tunnels, as well as for bridges. However, for the solution of these problems, time history analysis is required, and this is usuall...

Results of a parametric study on earthquake time history response of asymmetric single storey structures with one axis of symmetry modelled as two degree-of-freedom systems are compared with static seismic code provisions. A large number of such systems with a range of mass centre to rigidity centre eccentricities, a range of uncoupled lateral natu...

This paper presents the results of an investigation on drift reduction in uniform and non-uniform belted structures with rigid outriggers under several lateral load distributions which are likely to be encountered in practice. Design aids in the form of graphical presentations of the somewhat complex solutions are provided to assist the practicing...

A simple plane frame model is described for the lateral load analysis—static and dynamic—of frames in multistory buildings including biaxial load effects. By taking advantage of the shear force-axial force and the torque-bending moment analogies it is possible to model the spatial behavior of the structure, and to consider the combined effects of b...

The importance of primary and secondary stresses on the strength of statically loaded triangulated trusses having rigid joints is reviewed. Support is given to the contention that accurate modelling of material properties and member end conditions is justified both for predicting overall failure loads and for assessing the sequencing through which...

Several continuum methods for torsional analysis of slender perforated cores are described. First, the open section torsion-bending theory, which neglects shear deformations, is described. It is then modified to consider shear deformations that become important with increasing lintel stiffness. To avoid the warping incompatibility, of the open sect...

Effects of alternative designs of bilinear base isolation systems on the seismic response of ten, five and two-storey shear buildings, with one axis of symmetry consisting of three parallel frames, are investigated. Analyses with the El Centro and Taft records predict appreciably lower shear forces and torques compared with the unisolated case, whe...

A simple formula is presented for computing the loss in carrying capacity of axially loaded short reinforced concrete columns due to the nominal eccentricity stipulated by the Israeli Concrete Code (Israel Standard 466 Pt. 2, 1978). This formula confirms and generalizes earlier published results.

Simple procedures are proposed for computing response spectra for torsional and rocking input ground motions assuming horizontally travelling waves of constant shape. It is shown that harmonic relationships exist between the rotational spectra and the corresponding translational spectra, and that SV rather than PSV is the correct basis for deriving...

A simple approximate step-by-step method is proposed for the nonlinear analysis of fastener groups subject to eccentric shear. The procedure replaces the traditional trial and error solution by a series of incremental linear elastic analyses. Rigid plate-piecewise linear bolt model is assumed. Conservative, yet sufficiently accurate results may gen...

A relatively simple method to determine the shear center of asymmetric open thin-walled sections is presented. The method is based on the use of two nonorthogonal directions of loading which produce mutually perpendicular neutral axes coincident with the x and y axes respectively. The load direction and the neutral axis are shown to be 'conjugate a...

It is shown that the torsional analysis of tube structures can be performed directly by means of standard plane frame or plane stress finite element computer programs rather than by three-dimensional procedures. By considering in-plane rigidity of the floor slab and the presence of an elastic axis, it is shown that the only modifications required i...

Computer oriented and manual procedures are presented that enable a direct second order analysis of asymmetric building structures to be performed by means of first order formulation. This is achieved by modeling the geometric-stiffness of the structure as a fictitious column with negative lateral and torsional stiffness properties. Simplified meth...

During the 9 February, 1971 San Fernando earthquake, Building 41 of the Veterans Administration Hospital was in an area of very strong snaking; being directly over a portion of the causative fault; it is estimated that the building experienced a maximum base shear of 60 to 130 per cent of the weight of the structure. It survived with very minor str...

A simple technique is proposed that enables a direct second order analysis to be performed by means of first order plane frame computer programs. The geometric-stiffness matrix is modelled as a fictitious column with negative stiffness. The effect of additional moments due to eccentricity of axial force about the deflected shape is considered. The...

Structures which collapse or are heavily damaged in destructive earthquakes are analyzed by engineers to determine why they performed so poorly and to find out how their design could have been improved. However, it is equally important for buildings that survived exceptionally strong shaking to be analyzed and an explanation given as to why they we...

The flexural beam approximation commonly used for evaluating the vibration frequencies of sandwich beams is shown to be of limited applicability. A formula proposed for evaluating the fundamental frequencies of cantilever sandwich beams is generalised for higher modes and other boundary conditions, and is shown to be in very good agreement with exp...

A modal analysis procedure is presented for the seismic response of belted high-rise building structures within the framework of the response spectrum technique. The first 3-modes of vibration are considered. Natural periods, internal forces and deflections are computed, and design charts are presented for the parameters of interest. Based on Appli...

A simple procedure is proposed to evaluate the out-of-plane vibration frequencies for a class of horizontally curved beams. The two governing differential equations are first partly uncoupled by means of a linear transformation. When the remaining coupling terms cannot be neglected, a two-degree-of-freedom solution is obtained by taking advantage o...

It is shown that for a class of asymmetric building structures, a lateral load analysis can be performed by means of analogous plane frames rather than by a three-dimensional procedure. Based on a co-ordinate transformation, the technique is applicable to structures with two types of framing systems each comprising several vertical planar assemblag...

History of elastic static procedures for the seismic analysis of torsionally unbalanced building structures is briefly reviewed. It is suggested that the provisions of NZS 4203:1976, accounting for modal coupling, are based on inconsistent interpretation of results from well known two-degrees-of-freedom models. An alternative dynamic procedure is d...

The paper shows how the existing approaches to the dynamic analysis of asymmetric tall buildings, using a single story torsional coupling analogy, can be applied to a wide class of irregular structures and under what conditions. A step by step procedure using the response spectrum technique is outlined and illustrated by a numerical example. A thre...

A scheme is proposed to calculate the effect of torsion on each lateral load resisting element of asymmetrical buildings in the context of the response spectrum technique. The scheme consists of: (i) Obtain the modal shear and torque on the building by the response spectrum technique, (ii) Compute the total modal shear forces on each frame by resol...

In this note the numerical values of the three lower eigenfrequencies of the constrained cantilever are presented in a graphical form. These are given as functions of the rotational spring location along the beam for a large number of rotational stiffness ratios.

An efficient approximate hand method is proposed for the evaluation of the dynamic properties of asymmetric wall-frame structures. The approximation is based on a two-degree-of-freedom zeroth order solution of the coupled differential equations of motion. The restrictions on the structural geometry of the building imposed in a previous paper1 are r...

An approximate method is proposed for the dynamic analysis of torsionally coupled tall building structures by utilizing the properties of their uncoupled counterparts. An exact solution is first given for the particular case in which the lateral and torsional stiffness matrices are uncoupled by same transformation. The method is then applied to a w...

An approximate method is proposed for evaluation of the natural frequencies and mode shapes of uniform asymmetric wall-frame structures. An exact solution is first given for the case in which the coefficient matrix of the dynamic equilibrium equations satisfies certain conditions. Using perturbation analysis, the method is then applied to the more...

An approximate method for the dynamic earthquake analysis of coupled shear walls within the framework of design response spectra is proposed. The first three modes of vibration are considered and the dynamic loading associated with each is assumed to be represented by the corresponding mode of a vibrating cantilever. Based on this approximation, th...

Dunkerley's formula is shown to yield a lower bound for the fundamental frequency of vibration of a continuous elastic system whose flexibility is separable into a number of distinct components. The use of the formula is illustrated by considering a uniform cantilever and a three layer sandwich beam.

An approximate yet accurate formula is proposed for the natural frequencies of coupled shear walls under continuous medium assumptions. First the deflected shape of the structure is represented as the sum of two components: one due to flexural cantilever action and one due to shear-flexure cantilever action. The natural frequencies of the latter tw...

An approximate hand method is proposed for lateral force analysis of asymmetric wall-frame structures having constant properties along the height. The coupled torsion-bending differential equations of equilibrium are decoupled using an orthogonal transformation. The deformations and stress resultants in the wall and frame assemblies are obtained by...

A method is proposed for the analysis of a central column supporting uniformly loaded cantilevered stairs. Equations for determination of bending moments about two perpendicular axes for hinged and fixed support conditions are given. Tabulated results for these moments and their resultant are presented for the range of spiral turn angles encountere...

A simple method for torsional analysis of perforated core wall structures considering shear deformation is presented. The governing differential equation is derived from compatibility using open section thin-wall torsion-bending theory. The method is compared with conventional analysis in which shearing strains are ignored to show that for a narrow...

An approximate method is proposed for the torsional analysis of narrow rectangular grids supported along the short edges. Distributing the torsional rigidity of the transverse girders through their spacing and assuming rigid displacement of the cross-section, the solution is obtained by means of the familiar torsion-bending differential equation fo...

The seismic performance of building structures is a direct function of the maximum interstorey drifts which occur during strong seismic ground motions. Maximum drifts can be estimated using the concept of drift spectra. This paper presents a simple technique for deriving drift spectra for frame structures which is based on elementary shear-beam vib...

This paper presents the results of a comparison study performed between the numerically predicted and experimentally observed (through shaking table tests) dynamic behaviors of two scaled models of steel frame buildings structures: one symmetric and one asymmetric in plan. The shaking table tests were carried out at the Earthquake Engineering Cente...

Sumario: Lessons from past earthquakes -- Seismicity, seismic risk and strong motion -- Soil response and soil-structure interaction -- Response analysis -- Code oriented analysis -- Base isolation -- Strengthening of existing structures -- Various themes (Optimizational approach to identification of structural dynamic parameters basing on engineer...