Bowing of marble panels: on-site damage analysis from the Oeconomicum Building at Göttingen (Germany)

Abstract

The use of natural stone panels or cladding material for building facades has led to some durability problems, especially with marble slabs. To examine the effects of intrinsic and extrinsic parameters on bowing, a very detailed study was performed on the Oeconomicum Building at the University of Goettingen. In total 1556 panels from the whole building were measured with respect to bowing using a bow-meter. The variation of bowing ranges from concave (up to 23 mm/m) to convex (up to -11 mm/m). The variation is not controlled by the position with respect to the geographical coordinates, height above ground, shadows, temperature etc. On the north facade the different rock structures visible on the panel surfaces are a result of the marble slabs being cut in different directions. The different degrees of bowing are associated with the structure of the marble since all other influencing factors are relatively constant (position, temperature, moisture content, building physics). Experimental data on the expansion behaviour under dry and/or wet conditions reveal different degrees of bowing with respect to the rock fabric and may help to explain the observed differences in bowing. The effect of the rock fabric, especially of the lattice preferred orientation in this case, clearly controls the deterioration of the marble and the degree of bowing. The bowing is also characterized by an increase in the porosity, decreasing values of ultrasonic wave velocities and flexural strength. The loss of cohesion in the strongly deteriorated panels is clearly visible in the microstructure by the open grain boundaries which are interconnected to intergranular microcracks.

Bowing of dimensional granitic stones

“…The phenomenon is well known in marbles, having been observed in various scenarios from ancient gravestones (Grimm 1999) to modern buildings such as the Amoco building in Chicago, Oeconomicum building in Göttingen (Koch and Siegesmund 2002) or Finlandia Hall in Helsinki (Ritter 1992). A more recent summary of marble bowing is given by Siegesmund et al (2008a), in which the latest and the most important hypotheses debated in scientific literature are presented.…”

Salt-weathering simulations under hot desert conditions: agents of enlightenment or perpetuators of preconceptions?

“…Evidence for the effectiveness of this process at the scale of large rock blocks can be found not just in nature (e.g., see Folk and Begle-Patton, 1982) but also in unwitting experiments created by architects who clad buildings in sheets of stone with insufficient regard to stone structure and intervening expansion joints. Thus, for example, Koch and Siegesmund (2002) described the bowing of 128Â67-cm marble panels at the University of Gfttingen resulting from preferred thermal expansion dictated by rock fabric (grain size, grain boundary configuration, shape, lattice of preferred orientation, and microcrack fabric). Because the panels were cut without regard to this fabric, postemplacement heating and cooling resulted in a complex web of expansion and contraction that could only be accommodated by the inward and outward bowing of the panels.…”

Thermal stress in the Apuan marbles: Relationship between microstructure and petrophysical characteristics

“…Others [18][19][20][21] emphasised the importance of moisture, and concluded that exposure to heating alone is not sufficient to explain the expansion and bowing of marble cladding. Koch and Siegesmund [22], demonstrated that the moisture content after a heating cycle apparently influences the intensity of marble degradation. During the laboratory test, they demonstrated that the moisture content after a heating cycle has an impact on the strain rate of the Italian marble.…”