„DAMB” - Computer system of dynamic analysis of tall

buildings stiffened by shear wall structures

In Pozna University of Technology a computer system of

dynamic analysis of tall buildings with an arbitrary plan, stiffened by shear

wall structures and/or cores has been elaborated. Using the system it is

possible to determine the frequencies and mode shapes of free vibrations

and the dynamic response from input of seismic and paraseismic

influences for a wide range of multistorey buildings.

Methods of dynamic analysis of tall buildings stiffened by shear wall structures, currently

used in designing practice, allow for determination of frequency spectrum and mode shapes of

free vibrations with considerable approximation. As a consequence of this the dynamic response

of the building obtained from computations is approximate as well. At the Institute of Structure

Engineering of Pozna University of Technology there has been elaborated a computer system of

programs for the dynamic analysis of tall buildings stiffened by shear wall structures and/or cores

in order to make a more precise analysis of these complex structures possible.

Originally, the system was used on ICL 1900 and Odra 1300. At present it is possible to

take advantage of the system making use of computers compatible with IBM PC with medium

size operating memory and DOS standard operating system as well as Windows 3.1, Windows 95

and Windows NT environments. It is possible to analyse structures, the plan of which includes

walls, flexible joints and connected beams, located arbitrarily in the plan. Because of the fact that

more than half of the building mass is concentrated on the floor levels the dynamic structure

model with discrete masses in the form of floor slabs characterised by translational and rotational

inertias has been accepted. Floor slabs can be located on arbitrary ordinates along the building

height, according to the real distribution of floors in the building. Each floor can have a different

form and a different unit density. Structure stiffness is determined on the basis of exact solution of

differential equations describing displacements of 3-dimensional structure model. The coupled,

flexural - torsional structure vibrations are analysed.

Input data for computations using the DAMB (Dynamic Analysis of Multistorey

Buildings) system include the information about the shear walls, cores, connecting beams and

flexible joints, geometry and strentgh features of the structure which can be read from the

building plans. In order to determine the building mass you only need to give: one number

characterising density per volume of walls and connecting beams material and for all types of floor

slabs the floor density with a unit surface and a set of points determining the floor outline. Floors

with an arbitrary plan and holes are allowed (Fig. 1). The movement of the foundation is

determined by giving parameters of design response spectrum. On the basis of the data

determined in this way the system generates the mass matrix and the flexibility matrix for the

structure. Owing to replacement of numerical integration by integration according to analytically

introduced formulas and the best use of memory on magnetic discs, short computation times have

been obtained. The elaboration of macro-command of operating system, the data number being its

only parameter, makes use of the system really simple. Using the system allows for determination

of frequency spectrum and the mode shapes of free vibrations as well as the dynamic response of

the structure subject to seismic and paraseismic influences in a short time and at a relatively low

cost.

The above-described DAMB system of computer programs was elaborated in the eighties,

partly within the grant No 05.12 coordinated by the Institute of Fundamental Technological

Research of the Polish Academy of Sciences in Warsaw. The system was tested thoroughly. The

results of the computations obtained by using the system were compared, among others, with the

values obtained experimentally, presented in the literature. In 1984 operational use was begun.

Since then calculations concerning buildings being designed and the existing or erected ones,

which are with vibrations hazard, have been made in Wielkopolska, Warsaw and Sofia. The

system is being improved and developed continuously. The research has been focused currently

on the development of the analysis taking into account a non-linear model of the structure

material and impulse loads.

Fig.1. 3-D shear wall structure

1 - shear wall, 2 - connecting beam, 3 - floor slab