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Modelling influence

• f paraseismic tremors
• n precast apartment buildings

Jacek Barański, Piotr Berkowski, Grzegorz Dmochowski, Faculty of Civil Engineering Wrocław University of Technology Poland

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

Modelling influence of paraseismic tremors

• n precast apartment buildings

Presentation plan

• Introduction
• Description of selected types of precast

buildings

• FEM static and dynamic modelling
• Model of dynamic calculations
• Final remarks

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

I n t r

• d

u c t i

• n

Phenomena that occur in copper mining areas in Poland are as follows:  abasement of terrain, slope of terrain, and creep of soil surface

• they have no decisive influence on the technical condition of

buildings and structures

 ground vibrations caused by mining tremors, generally described using velocity and acceleration of soil vibrations

• they cause cracks in structural elements or at the contact surfaces

between different structural elements or materials

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

T y p e s

• f

b u i l d i n g s

WWP (Wrocław large plate) building system:

• typical height of 5 or 11 storeys
• foundations are made in the form of concrete continuous

footing or foundation plate

• basement walls are made as monolithic ones
• internal transversal bearing walls are 14 cm thick
• vertical edges are finished with the so-called “locks” with

reinforcing steel bars left, both elements made with aim to create vertical cores filled with concrete during assembly

• horizontal edges are provided with two steel bolts, helping

to stabilize and mount higher storey walls; filled with cement mortar

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

T y p e s

• f

b u i l d i n g s

WWP building system:

• gable walls are designed as three-layer ones with total

thickness of 21 cm and with reinforced 12 cm thick concrete bearing layer

• curtain walls, also the three-layer ones, are precast ones

with a thickness of 16 cm, with reinforced concrete bearing layer 5 cm thick

• floor slabs are 14 or 16 cm thick; typical floor span (load-

bearing wall spacing) was 2.4, 3.0, 4.8 and 5.4 m

• plates are reinforced in one direction, as being based on

the vertical walls on the opposite ends only.

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

T y p e s

• f

b u i l d i n g s

WWP building system:

Horizontal plan of WWP building with strengthening

STRENGTHENED LONGITUDINAL WALLS

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

T y p e s

• f

b u i l d i n g s

WBL (Wrocław block) building system:

• transversal load-bearing wall system is used
• floor slabs are based on the external gable and internal

bearing walls

• height of these buildings is up to 8 or 10 storeys
• underground

storeys are constructed from precast elements or made as monolithic ones

• walls are made of full or hollow precast blocks
• ground

floor concrete walls are 24 cm thick with longitudinal circle channels

• floor slabs are also hollow ones with 24 cm of thickness;

plates are canted on the ends what allowed the realization of ring beam

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

T y p e s

• f

b u i l d i n g s

WBL (Wrocław block) building system:

Horizontal plan of WBL building

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP 2D & 3D building model:

• model was prepared in two stages, using the standard

LUSAS program elements:  in the first stage 2D model of the 11-storey building was created:

• in place of all the structural horizontal joints 2D elastic

elements "joint2D” were introduced

• bearing lateral walls system of the building was replaced

by beam elements with equivalent geometric characteristics

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP 2D & 3D building model:

• system was tested for dead and wind loads and uneven

settlement in the longitudinal direction of the building

• during the calculation static system of structure was

changed by changing stiffness of “joint2D” elements

• influence of curtain walls and technological service loads

were not taken into account

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP 2D & 3D building model:  the second model was a fully 3D model of a building constructed in the WWP system

3D FEM model

• f

precast WWP building

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP 2D & 3D building model:

• bearing carrying system was modeled with help of rigid

floor slabs and load bearing vertical walls based on them in transversal direction

• in

the longitudinal direction sections

• f

walls along stairways were also the bearing elements

• support of building was modeled as the fixed one in all of

the examples

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP 2D & 3D building model:

• in the model the walls were not connected to the floor slabs

directly, but by using elements of "joint3D", analogous to "joint2D”, but working in the spatial layout. Using them horizontal joints in three dimensional space were modeled.

• examples of calculations under action of wind, uneven

settlement and paraseismic tremors were realized

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP primary joint model:

• primary joint model was geometrically identical with the

typical horizontal joint used in precast WWP building system

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP primary joint model:

• 3D elements

with 8 nodes were applied as finite elements

Primary model – results of

x

stresses – beginning phase.

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP primary joint model:

• nonlinear analysis was

carried out using built-in LUSAS FEM System multi-crack concrete Jefferson model

Primary model – results of

x

stresses – failure phase Failure mechanism starts in the middle of the joint

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP substitute joint model:

• primary model ocurred

useless for large models analysis because of complicated form

• substitute model was

built with LUSAS finite element called “joint” containing translational and rotational springs

LUSAS FEM substitute model

• f

joint between precast elements

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP substitute joint model:

• “joint” characteristics,

as spring stiffness, were calculated according to the primary model

• element was suitable for

static and dynamic analysis when was applied to substitute part of the horizontal joint

FEM model

• f

whole horizontal joint

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

S t a t i c & d y n a m i c F E M

FEM WWP substitute joint model:

• by changing the stiffness of each spring it was possible to

simulate different states of the whole horizontal joint – i.e. the connection of wall and slab elements – from monolithic to hinge one, with possibility of sliding, which is a good approximation of damaged elements in real prefabricated building

• analyses was carried out considering cracks and stress

distribution in horizontal joints

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

D y n a m i c a n a l y s i s

FEM dynamic calculation model:

• Three main building models were taken into

consideration:

• 1st – with ideal horizontal joints
• 2nd – with degenerated horizontal joints
• 3rd – strengthened construction
• Natural frequency analysis was carried out for models
• Spectral repsonse analysis was realized
• Dynamic analysis was conducted

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

D y n a m i c a n a l y s i s

FEM dynamic calculation model:

• Results of natural frequency analysis for 3 models

To diagnose the dynamic state

• f the building a global damage

coefficient dM, (DiPasquale & Çakmak), was used:

M = 1-TM/T0

T0 – first natural period of an ideal building TM – first natural period of a building with strengthening

• r damaged joints

Corresponding values of

M were:

• for the 2nd building model – 0.885
• for the 3rd one – 0.241

The results show the global change of dynamic characteristics comparing with an ideal building.

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

D y n a m i c a n a l y s i s

FEM dynamic calculation model:

• Spectral response analysis
• to prepare adequate dynamic

loads LUSAS FEM system uses spectral response method, so a read-out from an accelerometer is needed to determine a spectral curve

X axis shows time of the quake in sec and Y axis an amplitude

• f

an acceleration in m/sec2

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

D y n a m i c a n a l y s i s

FEM dynamic calculation model:

• Dynamic analysis
• data from spectral curve

entered into the Lusas System, allows loading the structure with a kinematic loads. System uses the CQC (Complied Quadratic Combination) method to calculate the building response.

X axis shows frequency in Hz and Y axis an amplitude of an acceleration in m/sec2

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

D y n a m i c a n a l y s i s

FEM dynamic calculation model:

• Dynamic analysis
• comparing displacements and stresses in characteristic

nodes for different structures (it means with different state of joints) it is possible to diagnose which building is more flexible on a tremor and also to define if the strengthening system is well designed

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

D y n a m i c s n a l y s i s

FEM dynamic calculation model:

• Dynamic analysis
• note: tremor with smaller value of acceleration can evoke

bigger displacements

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

F i n a l r e m a r k s

Final remarks:

• Response of the building structure not only depends
• n the maximum value of ground acceleration but also
• n the frequency corresponding to this acceleration

and natural frequencies of building structure.

• To diagnose properly if a tremor is dangerous for a

building

• ne

must know all the parameters

• f

a structure and also all the parameters of tremors.

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events

F i n a l r e m a r k s

Final remarks:

• If paraseismic tremors, even „small”, occur often

they may lead to slow degradation of the so-called “weak points” in building structures, especially if the buildings are made from precast concrete elements which have mixed cement-mortar and steel bar joints between them.

• Numerical

model

• f

such a structural joint

• f

elements in precast building was presented. Along with structure technical state diagnosis it was used to define the real structural response to paraseismic tremors.

THANK YOU VERY MUCH FOR YOUR ATTENTION !

Modelling influence of paraseismic tremors

• n precast apartment buildings

COSTC26 Conference: Urban Habitat Constructions under Catastrophic Events