Zdeněk P. Bažant

Zdeněk P. Bažant
Born	(1937-12-10) December 10, 1937
Alma mater	Czech Technical University Czechoslovak Academy of Sciences Charles University
Occupation	professor, engineer, scientist
Employer	Northwestern University
Awards	Austrian Cross of Honor von Karman Medal Timoshenko Medal Prager Medal Nadai Medal, etc.
Website	www.civil.northwestern.edu/people/bazant/

Zdeněk Pavel Bažant (born December 10, 1937) is McCormick School Professor and Walter P. Murphy Professor of Civil Engineering and Materials Science in the Department of Civil and Environmental Engineering at Northwestern University's Robert R. McCormick School of Engineering and Applied Science.^[1][2]

Education, career and academic positions

Born in Prague on December 10, 1937, Bažant received the degree of Civil Engineer from the Czech Technical University (CTU) in Prague in 1960. While employed as Bridge Designer he earned in 1963 (as an external student) a PhD in engineering mechanics from the Czechoslovak Academy of Sciences; in 1966, he earned a postgraduate diploma in theoretical physics from Charles University, Prague. During 1964–67 he was research assistant professor at CTU working on fiber composites, and obtained the degree of Docent habilitatis in Concrete Structures from CTU in 1967. After postdoctoral fellowship at CEBTP Paris (1966–67) and Ford Foundation fellowship at University of Toronto (1967–68), he was during 1968–69 Associate Research Engineer at the University of California, Berkeley. In 1969 he joined Northwestern University as an Associate Professor and became Professor of Civil Engineering in 1973. During 1981–87 he served as the founding Director of Center for Geomaterials. During 1974-1994 he was simultaneously a Staff Consultant at Argonne National Laboratory. Since 1990, he has held the Walter P. Murphy Chair in Civil and Mechanical Engineering and Materials Science, and since 2002 simultaneously the chair of McCormick Institute Professor. Bažant served as the president of the Society of Engineering Science (1993); was the founding President (1991–93) of the International Association of Fracture Mechanics of Concrete Structures (IA-FRAMCOS); and the founding President (2001-2002) of the International Association of Concrete Creep and Durability Mechanics (IA-CONCREEP).^[2] He served as Division Director in IA-SMiRT (Struct. Mech. in Reactor Technology), as member of the US Nat. Comm. on Theor. and Applied Mech., and as editor-in-chief of Journal of Engrg. Mechanics of the Am. Soc. of Civil Engers. (ASCE). He has een the US regional editor of Int. J. of Fracture. He has been the US regional editor of Int. J. of Fracture.

Research contributions and impact

Bažant, who is "generally regarded as the world leader in research on scaling in the mechanics of solids",^[2] is the author of six books dealing with concrete creep, stability of structures, fracture and size effect, inelastic analysis and scaling of structural strength. He is an Illinois registered Structural Engineer, and is one of the original top 100 ISI highly cited researchers in engineering (of all fields, worldwide). As of June 2015, his H-index is 103, i10 is 496, and total citations 46,000 (on Google, minus self-citations).

Honors and awards

Bažant was elected to US National Academy of Sciences in 2002, US National Academy of Engineering in 1996, and American Academy of Arts and Sciences in 2008. He is a foreign member of the Royal Society of London (2015), Austrian Academy of Sciences, Academy of Engrg. of Czech Rep., Italian National Academy (dei Lincei, Rome), Spanish Royal Academy of Engrg., Istituto Lombardo (Milan), Academia Europaea (London) and European Acad. of Science and Arts. His honors include 7 honorary doctorates: CTU Prague (1991), TU Karlsruhe (Fredericiana, 1997), UC Boulder (2000), Politecnico di Milano (2001), INSA Lyon (2004), TU Vienna (2006), and Ohio State University Columbus (2011). He is a Honorary member of Am. Soc. of Mechanical Engineers (ASME), Am. Soc. of Civil Engineers (ASCE), Am. Concrete Institute (ACI), RILEM, Paris (Int. Union of Res. Lab. In Mat. & Str.), Czech Soc. of Mechanics, Czech Soc. of Civil Engineers, Czech Concrete Society, and Building Res. Institute of Spain. He has given almost one hundred plenary lectures at major conferences and over thirty distinguished university lectures. His honors include:

Books

• Bažant, Zdeněk P. (1966). Creep of Concrete in Structural Analysis. ((in Czech), Prague: State Publishers of Technical Literature (SNTL).
• Bažant, Z.P., and Cedolin, L. (1991). Stability of Structures: Elastic, Inelastic, Fracture and Damage Theories, Oxford University Press, New York; 2nd. ed. Dover Publications, New York 2003; 3rd ed. World Scientific Publishing, Singapore--New Jersey--London 2010.
• Bažant, Z.P., and Kaplan, M.F. (1996). Concrete at High Temperatures: Material Properties and Mathematical Models, Longman, 2nd ed. Pearson Education, Edinburgh, 2002).
• Bažant, Z.P., and Planas, J. (1998). Fracture and Size Effect in Concrete and Other Quasibrittle Materials. CRC Press, Boca Raton and London
• Jirásek, M., Z.P. Bažant (2002). Inelastic Analysis of Structures. London and New York: J. Wiley & Sons.
• Bažant, Z.P. (2002). Scaling of Structural Strength, Hermes Penton Science (Kogan Page Science), London; 2nd updated ed., Elsevier, London 2005.
• Bažant. Z.P., and Le, Jia-Liang (2017). Probabilistic Mechanics of Quasibrittle Structures: Strength, Lifetime and Size Effect. Cambridge University Press, Cambridge, U.K.

Selected Papers

• Z.P. Bažant and B.-H. Oh (1983). “Crack band theory for fracture of concrete.” Materials and Structures (RILEM) 16: 155-177 (>2600 cit. on Google by 2016; though journal not scanned by ISI prior to 1995).
• Z.P. Bažant (1984). “Size effect in blunt fracture: Concrete, rock, metal”. ASCE J. of Engrg. Mechanics 110: 518-535.
• G. Pijaudier-Cabot and Z.P. Bažant, Z.P. (1987). “Nonlocal damage theory.” ASCE J. of Engrg. Mechanics, 113 (10): 1512—1533
• Z.P. Bažant and G. Pijaudier-Cabot (1988). ``Nonlocal continuum damage, localization instability and convergence." ASME J. of Applied Mechanics, 55, 287—293
• Z.P Bažant (1988). Mathematical Modeling of Creep and Shrinkage of Concrete (editor, wrote two chapters), J. Wiley, Chichester
• Z.P. Bažant, T. Belytschko and T.-P. Chang (1984). “Continuum theory for strain softening.” ASCE Journal of Engineering Mechanics, 110 (1984): 1666-1692
• Z.P. Bažant (1976). “Instability, ductility, and size effect in strain softening concrete”. ASCE Journal of Engineering Mechanics 102: 331-344.
• Z.P. Bažant and M. Jirásek (2002). “Nonlocal integral formulations of plasticity and damage.” ASCE J. of Engrg. Mechanics 128: 1119-1149.
• Z.P. Bažant and L.F. Estenssoro (1979). “Surface singularity and crack propagation.” Int. J. of Solids and Structures 15: 405-426.
• Z.P. Bažant and M.T. Kazemi (1990). “Determination of fracture energy, process zone length and brittleness number from size effect, with application to rock and concrete.” Int. J. of Fracture, 44: 111-131.

Selected Recent Papers

• Z.P. Bažant, M. Salviato et al. (2014). "Why fracking works." ASME J. of Applied Mechanics 81 (Oct.), 101010-1-101010-10 (posted on www.iMechanica.com; >2000 downloads within 3 weeks).
• Z.P. Bažant and F.C. Caner (2014). ``Impact comminution of solids due to local kinetic energy of high shear strain rate: I. Continuum theory and turbulence analogy." J. of the Mechanics and Physics of Solids 64, 223—235.
• F.C. Caner and Z.P. Bažant (2013). ``Microplane model M7 for plain concrete: I. formulation." ASCE J. of Engrg. Mechanics 139 (12), Dec., 1714–1723.
• Z.P. Bažant and J. Vorel (2014). "Energy-conservation error due to use of Green-Naghdi objective stress rate in commercial finite-element codes and its compensation." ASME J. of Applied Mechanics 81 (Feb.), pp. 021008-1 -- 121008-5.
• J.-L. Le and Z.P. Bažant (2014). ``Finite weakest-link model of lifetime distribution ofquasibrittle structures under fatigue loading." Mathematics and Mechanics of Solids 19(1), 56—70.
• Bazant, Z.P., and Su, Yewang (2015). "Impact comminution of solids due to progressive crack growth driven by kinetic energy of high-rate shear." ASME J. of Applied Mechanics 82 (March), pp. 031007-1--031007-5.
• Kirane, K., and Bažant, Z.P. (2016). "Size effect in Paris law and fatigue lifetimes for quasibrittle materials: Modified theory, experiments and micro-modeling." Int. J. of Fatigue 83, 209–220.
• Kirane, K., Salviato, M. and Bažant, Z.P. (2016). "Microplane-triad model for elastic and fracturing behavior of woven composites." Journal of Applied Mechanics ASME 83 (April), pp. 041006-1---041006-14 %(doi: 10.1115/1.4032275]).
• Salviato, M., Chau, Viet T., Li, Weixin, Bažant, Z.P., and Cusatis, G. (2016). "Direct testing of gradual postpeak softening of fracture specimens of fiber composites stabilized by enhanced grip stiffness and mass." J. of Applied Mechanics ASME 83 (Nov.) 111003-1---111003-16; doi:10.1115/1.4034312.
• Bažant, Z.P., Luo, Wen, Chau, Viet T., and Bessa, M.A. (2016). "Wave dispersion and basic concepts of peridynamics compared to classical nonlocal models." J. of Applied Mechanics ASME 83 (Nov.) 111004-1---111004-16 (doi: 10.1115/1.4034319).
• Chau, Viet T., Bažant. Z.P., and Su, Yewang (2016). "Growth model for large branched 3D hydraulic crack system in gas or oil shale." Philosophical Transactions of Royal Society A 374 (issue 2078, Oct.), pp. ... (doi: 10.1098/rsta.2015.0418).
• Bažant, Z.P., and Rahimi-Aghdam, S. (2016). "Diffusion-controlled and creep-mitigated ASR damage via microplane model: I. Mass concrete". J. of Engineering Mechanics ASCE 142 (10); pp. 04016108-1--04016108-10; DOI: 10.1061/(ASCE)EM.1943-7889.0001186.
• Sinko, R., Vandamme, M., Bažant, Z.P., Keten, S. (2016). "Transient effects of drying creep in nanoporous solids: understanding the effects of nanoscale energy barriers." Proc. Royal Soc. A 472:20160490; doi: 10.1098/rspa.2016.0490.
• Rahimi-Aghdam, S., Bažant, Z.P., and Qomi, M.J.A. (2017). "Cement hydration from hours to centuries controlled by diffusion through barrier shells of C-S-H." J. of the Mechanics and Physics of Solids 99, 211-224.

Scientific and Technical Contributions

    Zdeněk Bažant’s main focus is on mathematical modeling  in mechanics of materials and structures. He has made significant contributions to several important engineering fields. E.g., in 1976 he showed by stability analysis that the concept strain-softening (then regarded by mechanics gurus as “insane”) does make sense if there is a finite material characteristic length that limits strain localization. Then, in 1983, he published a paradigm changing paper on the crack band model, which presented a simple way to handle nonlocal damage and avoid spurious mesh sensitivity. Both papers were hardly cited for two decades but then the citations exploded (even though the 1983 paper was declined in a  premier American journal and then published in a French journal little known at that time; the citations of this papers now run several hundred a year and in 2016 exceeded 2600, on Google). The crack band model is now embedded in various commercial programs and is applied in user’s subroutines for concrete, rocks and comosites, and is the mainstay in design of large commercial composite airframes (e.g., at Boeing).
    
    It was similar with Bažant’s (by now classical) material models for nonlocal damage, for energetic (non-statistical) size effect in quasibrittle fracture, for microplane constitutive modeling, for a solidifying material model for concrete creep, for calculations of moisture diffusion in nano-pores of concrete, and for his solution of elastic three-dimensional singularities at skew intersections of crack front line with a surface. They all became highly cited only recently. So did. his   monumental treatise on stability of structures, innovative in treating the stability of fracture and damage, thermodynamics of structural stability, and objective stress rates for 3D bodies. Ditto his pioneering books on fracture and size effect in concrete, on concrete at high temperatures, and on concrete creep and shrinkage.  Bažant is best known as the world leader in scaling research in solid mechanics. Bažant size effect law, with his demonstrations (mainly in six papers during 1976-91) of damage localization instabilitites and of spurious dependence of the early strain-softening models on element size, took a long time to sink in. But eventually it changed the design computations in concrete and geotechnical industry, and impacted the design practice in fiber composites (for large aircraft, ships and, car crashworthiness). The RILEM standard  recommendation for testing of fracture energy and characteristic length of concrete (FMT/1990) is based on Bažant’s law.  
    
    Later Bažant extended his scaling research to statistical size effect. Exploiting the frequency law of interatomic bond breaks, he showed that, due to fracture process zone finiteness, the statistical strength of quasibrittle structures follows a graft of Gauss and Weibull distributions and exhibits a strong size effect, causing the safety factors and static and fatigue lifetimes of quasibrittle structures to be size dependent. He demonstrated that disregard of size effect was a major factor in many structural failures. His proposals of code provisions taking into account the size effect on shear failures of beams and slabs has been endorsed by ACI Committee 446 but not yet accepted for the ACI concrete design code.  
    
    Bažant’s microplane model for softening damage in concrete, rocks, composites, etc., in which the constitutive law is written in terms of  stress and strain vectors on a generic plane, trades conceptual simplicity and clarity of physical interpretation for higher computational demands, which initially stifled applications but recently ceased to be an obstacle. The microplane model is now included in large-scale computer codes at U.S. national labs (EPIC, PRONTO, etc.) and in various commercial codes (ATENA, DIANA, SBETA, OOFEM). His microplane model for jointed rock is embedded, e.g., in ANSYS. With the microplane model, Bažant was able to capture the `vertex’ effect in softening damage, which is important for dynamics but cannot be simulated with the classical tensorial constitutive models (for concrete he also demonstrated by tests). He showed experimentally and theoretically that material strain softening reverses to hardening when the loading rate suddenly increases.  
    
    Bažant further made major theoretical and experimental contributions to the sustainability problems of infrastructure, to high temperature effects in nuclear containments and in tunnels exposed to fire, to thermodynamics and nano-mechanics of creep and shrinkage in hydrating cement, and to 3D singularities at fracture surface intersections. His Model B3 for practical prediction of concrete creep and shrinkage, calibrated by a worldwide database of thousands of laboratory tests assembled by his assistants, became an international standard recommendation (RILEM-CGS/1991). His nonlinear diffusion model for concrete is featured in Eurocode and widely used in durability analysis. His simple age-adjusted effective modulus method for concrete structure taking into account multi-decade chemical aging is embedded in the Eurocode as well as ACI standard recommendation. His unconditionally stable ‘exponential’ algorithm for rate-type concrete creep law is now standard in structural computations.  
    
    In finite strain theory and structural stability analysis, Bažant was the first to resolve the decades-old controversy about the 3D stability theories of Engesser, Haringx, Hencky, Truesdell, Biot, etc., as applied to soft-in-shear structures. In 1971, he showed by energy variational analysis that these theories correspond to different choices of objective stress rate and are all equivalent upon certain transformations of the tangential elastic moduli, and that some objective stress rates used in Abaqus, Ansys, LS-Dyna and other  commercial codes do not conserve energy. This 1971 result was generally ignored until, a few years ago, Bažant demonstrated that the energy conservation error is non-negligible and can be of the order of 100% in the case of highly orthotropic structures, orthotropic damage, or high compressibility. Furthermore, he provided a coherent mechanical explanation of the collapse of WTC Towers in New York, and then derived the crush-down and crush-up differential equations of progressive collapse of tall buildings.  
    
    Bažant also developed a theory of the destructive alkali-silica reaction (ASR) in concrete (including the diffusion of expanding gel) which matches test results; a theory on hundred year prediction of concrete creep based on inverse analysis of observed excessive bridge deflections, coupled with Bayesian extrapolation of short-time test data; and predictions models B3 and B4 for concrete creep and shrinkage (both drying and chemical-autogenous) which became standard international recommendations of RILEM. He also formulated new theory chemical aging due to cement hydration from hours to centuries at variable temperature and humidity, and a theory for of microprestress (eigenstress) in hydrated cement originating from disjoining pressures of hindered adsorbed water in nanopores. He extended his probabilistic theory of quasibrittle failure to the size effect on residual strength and lifetime, and on Paris law the cyclic crack growths in quasibrittle materials, and showed an analosy with dielectric breakdown. He demonstrated his non-statistical size effect for the fracture of bones and of dental materials.  
    
    Recently, with his motivated group of assistants, Bažant works on stability and propagation of hydraulic fracture in gas or oil shale and mitigation of environmental risks of fracking; on size effect in fatigue crack growth in quasibrittle materials; and on energy absorption in composite crush cans for cars. Considering the body forces do to water diffusing into shale pores, he showed that hydraulic fracture must branch laterally, and determined their spacing inversely, based on gas production observations. He formulated a new theory of comminution of solids under impact due to release of kinetic energy of high-rate shearing, analogous to turbulence. He examined critically the new theory of ‘peridynamics’ and showed its limitations.  Bažant strives in his contributions for practical relevance, originality, clarity and mathematical simplicity. Despite engaging in some super-computer simulations, he prefers analytical approaches as a way to reach deeper understanding, even at the cost of inevitable simplifications. At the same time, he has always extensively validated his results by experimental data and, when facing a vacuum of experimental evidence, conducted a host of innovative experiments with his own research team.  
    
    By 2016, Bažant’s H-index reached 112, i10-index 550 and his total citations 54,000 (on Google Scholar, incl. self-cit.).

References

Bibliography