50 Symposium Bucharest 07 048 Rus

International Symposium on Strong Vrancea Earthquakes and Risk Mitigation Oct. 4-6, 2007, Bucharest, Romania

STRUCTURES WITH HIGH SEISMIC RISK PASSENGER BUILDING - FOCŞANI

Anca I. Rus1, Aurel Ardelea2, Cristian S. Bălan3, Helmut H. Köber4, Carmen I. Bucur5

ABSTRACT Due to its geographical position, Romania is crossed by three of the ten trans-European transport corridors: Corridor IV Helsinki branch IVC, Corridor VII the Danube and Corridor IX Helsinki. As a consequence, a vast rehabilitation and modernizing program for the entire transport infrastructure has been recently commenced.

The present paper presents one of the newly designed structures for the passenger Railway Station building in Focsani, located along the Corridor IX Helsinki, very close to the well known Vrancea seismic focus.

The general layout of the structure is the result of solving the functional problems of the station so that the building had to be designed as four subassemblies of different dimensions separated by construction joints. As the building is made up of the four volumes, special problems related to the seismic characteristics and conformation of those, as well as technical solutions for the joints have to be conveniently solved.

Main aspects presented in the paper: selection of favourable lay-outs of the structures, both in plan and vertically, providing appropriate stiffness in order to keep the lateral displacements due to the seismic actions within the code prescribed limits, controlling the structural elements susceptible to be strained in the post-elastic domain etc.

This work is a continuation of the paper “Structures with high seismic risk – Case Study – Passenger Building, Romania” presented at International Symposium - Durability and maintenance of concrete structures, 2004 Croatia. In 2004 the building was under construction. Now the passenger building is in service and new aspects are included in the paper.

INTRODUCTION Due to its geographic position, Romania is crossed by three of the ten European transport corridors: Corridor IV Helsinki - branch IVC, Corridor VII Dunărea and Corridor IX Helsinki, Fig. 1 a, b [11, 12, Dragomir G., 2000]. Consequently, our country has initiated a large rehabilitation and modernization program for the entire transport infrastructure. One of the main targets is the rehabilitation and modernization of the railway stations to make them comply with the European standards and be able to operate for high-speed railway lines, according to UIC 413 norms and 140-0 ”Euro-stations”. This is also the case of Focşani station, Vrancea ‘s county town, placed along Corridor IX Helsink.

1 Drd. Structural Eng - Resistance – Architecture Division, Railway Study and Design Institute - Bucharest 2 Dr. Structural Eng Technical Consultant – Resistance – Architecture Division, Railway Study and Design Institute - Bucharest 3 Eng. - Technical Director – Building Design, Research and Software Institute – Bucharest 4 Dr. Eng. - Technical Consultant – Design Institute for Rolling Mill Bucharest 5 Prof. PhD. Structural Eng. - Department of Mechanics of Structures - Technical University of Civil Engineering – Bucharest

A. I. Rus et al. 352

a. b Figure 1.

The design of the seismic proof constructions is a complex one, as it implies a complex intersection of domains. Studies and information in domains as geology and seismology, geo-dynamics, construction materials and dynamics of structures are required.

PRESENTATION OF THE STRUCTURE

Architecture The new constructions are performed on the location of the old station. So, the allowed area had imposed dimensions and shape. The design and building activities focused on the passenger building as well as other utilities necessary for the station operation: canopy between the buildings, platforms, pedestrian tunnel. In addition it has performed also a systematization of the afferent areas such as “The railway station square” and boulevard starting from here, Fig. 2.

Figure 2. Model of the Assembly – view from the lines The building owes its shape to the joining and interference of four subassemblies having different dimensions in plan and vertically, Figs 3 and 4, [Rus A., 2004]. As: - Building block A is parallel with the railway lines and composed of three sections (A1, A2, A3) having different volumes with railway operation rooms as well as with commercial facilities. The central section A2 is B+GF+4F (basement + ground floor + 4 floors) is bordered by the lateral sections A1 and A3 having B+GF+1F (basement + ground floor + 1 floor), respectively GF+1F (ground floor + 1 floor).

International Symposium on Strong Vrancea Earthquakes and Risk Mitigation

353

Figure 3. The subassemblies

Figure 4. Passenger building in Focşani station - view from the tracks

a. during the construction work b. at the completion

Figure 5. Canopy placed between blocks A1-A2-A3


- The central hall developed on two levels and placed among the blocks A1-A2-A3, has

he ilt surface of 1325 m2 and a developed surface of 4800 m2.

ic focus, [Bălan Ş., 1982].

stem

ures have been taken to ensure right a-seismic conditions, aiming to get

l shape of the construction, regular compact and as far as

of the building part has lead to special

A2 and A3

the roof made out of light metallic structures – lattice beams with parallel flange; - Building block B is placed on perpendicular line on block A, and linked together by a

canopy at the ground floor level, Fig. 5. The height of this building block is GF+3F (ground floor + 3 floors).

whole assembly has a buT

articular issues when choosing the structural system P

ocşani town is placed in the close vicinity of Vrancea seismF

or the buildings subject to high intensity seismic actions, the choice of the structural syFis very important.

o, specific measSproper individual and general behaviour, [Marusciac D., 2000; Paulay Th., 1995; Bucur C., 1998; Fierbinţeanu V., 1999].

hen establishing the generaWsymmetrical shapes in places were chosen. Within the same section, evident dissymmetries were avoided in the volumes geometry, in the mass and rigidity distribution, in order to define the unfavourable effect of the general torsion.

he different dynamic response of the three sections Tstudy of the afferent joints among the parts. Their real dimensioning and execution has been carried the way to avoid any collision due to phase differences of the oscillations of the sections, Fig. 6.

Figure 6. View of the joints between sections


355

The sections A1, A2 and the block B are frames structures. The section A2 raised some problems due to the space which has been allotted in the assembly of the block A. Thus, the high ratio between the length (42.0 m) and the width (7.2 m) could led to unfavorable effects, such as: asynchronous seismic excitations of the foundation, significant general torsion, etc. Consequently, the mixed structure solution was chosen meaning frames and diaphragms. So, a construction which gathered the advantages of both systems has been created, such as: maintaining the functional flexibility provided by the frame structures and ensuring the required strength and the rigidity to take the horizontal actions provided by the structures in the diaphragms, Fig. 7.

Horizontal forces

Frames (shearing deformations)

Wall (bending deformations)

Frames and walls in ensemble

Figure 7. Shifting of the frames, structural works and dual systems at horizontal forces

REMARKS CONCERNING THE DUAL STRUCTURES SYSTEM

The dual system [Rus A., 2007], is usually used in composing the reinforced concrete structures. It is obtained either by continuing the structural works with frames not provided with wind bracing, or by connecting several structural with coupling girders. In Fig. 8 different dual structural systems are presented.

a) b) c) d)

Wall Wall WallWall

Figure 8. Structure of the dual system Although this type of structure is relatively used, there are few numbers of studies in the domain literature referring to their response to the seismic actions.

The main issue in studying a structure of dual system type consists in correctly estimating the contribution of each component. In Fig. 9, the results of a study, [Pauly Th., 1995] concerning the mode of taking over the overturning moment and the shearing force for a dual structure where the width of the wall lw varies. The considered loading is the horizontal equivalent seismic force.


1.0

Total shearing force

0.80.60.4 0.2 0 -0.2

E

2

4

6

8

10

12

1.0 0.8 0.60.40.20

Total moment

lw=4m

lw=6m

lw=8m

Leve

l

M/Mt Overthrow moments

V/VtShearing force of level

Taking over of the walls

Taking over of the frames

Taking over of the walls

Taki

ng o

ver o

f th

e fra

mes

Figure 9. Distribution of the overturning moments statistically estimated and also of the shearing forces at the first floor, on the structural walls and the frames of some dual systems (Pauly Th., 1995)

CALCULATION MODEL

Regarding the buildings assembly forming the railway station, the following presentations refer to the section A2, Figs 3 and 4. The functional requirements of the construction impose several resistance elements of irregular structure such as walls in which the hollows are not orderly placed. It is difficult to specify the behaviour of these elements and their modelling for calculation is not accurate enough to compared with the reality. For the calculation, the “method of the equivalent frame”, Fig. 10, was used which is one of the simplified method. The following approximations have been adopted: (i) the solid structural walls are considered in the computations as vertical cantilevers

embedded at the base; (ii) the structural walls with rows of door or window openings are considered in the computations as storied frames. For these frames, the following sections are considered: - (a) the vertical beams of the storied frames are the solid vertical areas of the walls

transformed into bars of constant section, - (b) the collar beams of the frames are transformed into bars with the theoretical span

equal to the distance between the axis of the vertical beams, having variable rigidity all along, namely: on the clear span of the opening, the sections are real; in the vertical beam area, the rigidity is infinite.


357

Figure 10. Equivalent frames The loads were grouped in four design hypotheses as follows:

(i) fundamental combination: - normal values = hypothesis 1; - design values = hypothesis 2;

(ii) special combination: - spectral load on the transversal direction = hypothesis 3; - spectral load on the longitudinal direction = hypothesis 4.

RESULTS AND COMMENTS

For the dynamic study, 9 eigenvalues of the vibration modes have been taken into account. In the table 1 are presented the vibrations periods values. The dynamic characteristics of the structures are the following: Mode 1 (T1 = 0.19s), transversal vibration; Mode 2 (T2 = 0.15s), longitudinal vibration; Mode 3 (T3 = 0.13s), torsion vibration. From dynamic point of view, the structure belongs to the type of rigid structures. To find out the spectral response – displacements and stresses – the structure was loaded with the design spectrum [9], Fig. 11, selected according to the location and taking into consideration all the other characteristics regarding the building importance, structure, materials, etc.


Table 1.

0

0.5

1

1.5

2

2.5

3

3.5

0

Mode Period (s) 1 0.19 2 0.15 3 0.13 4 0.05 5 0.045 6 0.036 7 0.026 8 0.024 9 0.019

=2.75β 0

Figure 11. Normal elastic response spectrum for the horizontal components of the acceleration for ground conditions explained by the corner periods: Tc = 1.0 and 1.6s [9].

Table 2 shows the spectral displacements in horizontal plan for some frames of the structure of the last two levels. Table 2. Displacements (m)

LEVEL 5 (altitude +17.75m) LEVEL 4 (altitude +14.15) Frames hypothesis 3 hypothesis 4 hypothesis 3 hypothesis 4

x 0.000277 -0.001644 0.000218 -0.001304 CT1 y 0.000964 0.000917 0.000729 0.000703

x 0.000240 -0.001626 0.000189 -0.001290 CT3 y 0.001512 0.000658 0.001152 0.000504

x 0.000413 -0.001707 0.000322 -0.001353 CT5 y 0.001982 0.000437 0.001515 0.000333

x 0.000413 -0.001707 0.000322 -0.001353 CT8 y 0.002687 0.000104 0.002060 0.000077

x 0.000413 -0.001707 0.000322 -0.001353 CT9 y 0.002922 -0.000007 0.002241 0.000009

x 0.000240 -0.001626 0.000189 -0.001290 CT10 y 0.003157 -0.000117 0.002423 -0.000094

x 0.000309 -0.001659 0.000242 -0.001315 CT12 y 0.003706 -0.000376 0.002846 -0.000294

x 0.000155 -0.001586 0.000123 0.001259 CL1 y 0.000964 0.000917 0.000729 0.000703

The importance class of the building is II [9]. This class includes constructions of special importance that require a reduction of the damages, considering their consequences. For hypothesis 3 the maximum displacements are 3.706x10-3 m for level 5 and 2.846x10-3 m for level 4, both at the cross frame 12, on the transversal direction of the building (Oy axis). For the hypothesis 4, the maximum displacements are 1.707x10-3 m for level 5 and 1.353x10-3 m for level 4 for more cross frames on the longitudinal direction of the building

0.5 1 1.5 2 2.5 3 3.5 4Perioada T , s

T D =2

8.8/T 2

4.4/T

T B =0.16

1.0s<Tc ≤ 1.6s ξ =0.05

T C =1.6s


359

(Ox). The condition required by the Romanian standards is that the maximum relative level displacement should be under 0.004 hlevel. As hlevel = 3.60 m, the allowed relative level displacement is 14.4x10-3 m. On the transversal direction of the building, the value of the maximum relative displacement is 3.096x10-3 m, respectively 1.274x10-3 m on the longitudinal direction. The technological joints, Fig. 6, are carried out in order to comply with all the conditions imposed by the regulations: seismic displacement, thermal extension and settlement. As a result, at the superstructure level, the joints between the sections are 0.10 m. The joints also continue at the infrastructure level, having smaller dimensions (about 0.02 m), Fig. 12. The joints are treated to comply with the architectonic design, so they are not visible.

a. during the construction work bb. at the completion

Figure 12. Joint continuated also at the level of the infrastructures One of the conditions to be fulfilled by the values of the dimensioning sectional stresses is that the size of the ration (ω) between the value of the ultimate bending moment and the value of the overturning moment from the seismic load should be at most equal to 4, [10]. Table 3 illustrates this condition.

Tabel 3

Cadru ω CT1 2.76 CT8 3.60 CL1 2.24

Additional reinforcement measures were required because there are two aspects, namely:

(i) reducing the negative effects of a possible general torsion due to the special shape in plan of the section A2, and

(ii) propping up the roof of the hall at level 3 (quota +10,55 m). So: (i) for the beams along the perimeter, additional reinforcements were introduced along their height, (ii) for the floorings, reinforcements were introduced both at the lower part and at the upper part, in the central part of the plate and at the supports, Fig. 13 a, b.


a. b.

Figure 13. Additional reinforcing

CONCLUSIONS

The location and the conditions imposed to the new railway station in Focşani town (Romania) make the design of the building assembly raise many problems as concerns the compliance, computation and performance, Fig. 14 a - f.

c. d.

a. b

.


361

e.

Figure 14. a, b, c, d, e, f Focsani Station building

The adopted technical solutions regarding the structure, compliance and resistance elements are entirely according to the technical regunorms, Fig. 15, a. b, c.

The most on the section A2. The conclusions for this section are the following:

(i) from dynamic point of view, the structure has a rigid behaviour, so the diaphragms contribution in the mixed assembly of the building is important;

(ii) the maximum relative level displacements are under the value required by the technical regulations;

(iii) the maximum absolute displacement is 3.706x10-3m at the maximum quota;

(iv) the technological joints are both at the superstructure level as well as at the infrastructure level

(v) are necessary additional reinforcements for the beams along the perimeter and for the floorings, at all the levels.

f. – presently in use

dimensioning of the lations correlated with Eurocode

a. b. c.

Figure 15 a, b, c. Passenger building in Focşani - European achievement

difficult design problems occurred


REFERENCES Bălan Ş., V. Cristescu, I. Cornea 1982 – Cutremurul de pământ din România de la 4 martie

1977 – Ed. Academiei Române Bucur C., A. Ardelea, N. Chivu 1998 - Repair and rehabilitation - Case studies - Three

Building of Bucharest, Romania - IABSE Colloquium Report IABSE- nr. de referinţă 2020, pag. 244-245/ ISBN 3-85748-094-8/Berlin, lucrarea pe CD – 1998 Berlin – Germania

Dragomir G., 2000 – European transport corridors. Romanian railway substructure modernising projects for Corridor IV – Helsinki – Revista Căilor Ferate Române nr. 1-2/2000, pp 3-7.

Fierbinţeanu V., A. Ardelea, C. Bucur, A. Rus, 1999 - Verificarea structurii unui acoperiş de tip paraboloizi hiperbolici Revista Căilor Ferate Anul 86 nr.5-6 / 1999 pp:52-57 ISSN 1220-868X

Marusciac D. şi alţii, 2000 – Proiectarea structurilor etajate pentru construcţii civile – Ed. Tehnica 2000, Bucureşti

Paulay Th., H. Bachman, K. Moser, 1995 - “Proiectarea structurilor din beton armat la acţiuni seismice”, Editura Tehnica –Bucureşti 1997

Rus A., 2007 – Studiul aplicării sistemului dual la construcţii noi şi existente – Referat 1 doctorat

Rus A., C. Bălan, H. Kober, C. Bucur, 2004 – Structures with high seismic risk – Case Study – Passenger Building, Romania - Durability and maintenance of concrete structures, International Symposium - Proceedings pp. 139-246, Ed. Secon HDGH - oct. 2004 Croatia

P100/2003 Cod de proiectare seismică a construcţiilor – proiect revizuire P100/92 – UTCB (P100.2006)

P85-2001 Cod de proiectare a construcţiilor cu pereţi structurali din beton armat – UTCB 2001

Proiect de execuţie Staţie Focşani – ISPCF – 2004 Site www. mt.ro/traceca/inde

50 Symposium Bucharest 07 048 Rus

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