Ultimate Energy Absorption Capacity Research Articles

Study on the impact resistance of polyurea-steel composite plates to low velocity impact

Experimental and numerical studies on the response of polyurea coated steel plates to low velocity impact of a cylindrical hammer are presented in this paper. Low carbon steel plates were made and coated with polyurea layers to enhance their impact resistances. The polyurea-steel composite plates were constrained by a test rig and impacted by a blunt cylinder hammer using a drop weight machine. Numerical simulations of the impact processes were performed using the finite element code LS-DYNA. The numerical simulation method was validated by comparing its results with the experiments’. The experimental results showed that the polyurea coatings can effectively improve the ultimate energy absorption capacity of the steel plates. The decreasing order of the ultimate energy absorption capacity of the composite plates when coated with same thickness of polyurea layers was: the upper-side-coated plates, the double-side coated plates and the lower-side-coated plates. In order to quantify the energy absorption efficiency of the composite plates, a parameter Ed was proposed, and it was found that the composite plate coated with 4 mm polyurea on its upper side had the greatest value of Ed among all the plates.

Experimental program and simplified nonlinear design expression for glass curtain walls with low-level blast resistance

A series of fi full-scale, nearly conventional, curtain wall specimens was tested in the UNC Charlotte Structures Laboratory. Specimens were subjected to quasi-static, uniform, out-of-plane loading to failure under displacement control. The tests were performed to obtain complete resistance curves, including the nonlinear behavior of the specimens up to ‘ultimate failure’. Ultimate failure was defi ned as mullion fracture or signifi cant breach of the curtain wall system when viewed as the protective barrier between building occupants and the external blast load. Representative load-defl ection and loadstrain resistance curves are presented. The energy absorbed by the curtain wall system up to three different limit states ‐ fi rst cracking of glass, fi rst yield of mullions, and fracture/breach of the system (ultimate failure) ‐ and maximum mullion end rotations are computed from the experimental results. Ultimate energy absorption capacity ‐ the recoverable linear strain energy plus the nonlinear energy due to formation of damage mechanisms ‐ and maximum mullion end rotations are essential for reliable and economical design of blast resistant curtain walls. To this end, a simplifi ed methodology is presented for analytically approximating curtain wall resistance functions that can be input to an energy expression that models nonlinear structural dynamic behavior due to an ‘impulsive’ loading. The blast resistance of a curtain wall can then be approximated using this procedure. It is shown that a nearly conventional curtain wall, a conventional system with two modifi cations ‐ use of laminated glass lites that are structurally glazed (wet-glazed) to a conventional framing system with structural silicone sealant ‐ had nearly 14 times the ultimate energy absorption capacity and nearly four times the blast resistance as the fully conventional system.

Age- and sex-related regional compressive strength characteristics of human lumbar vertebrae in osteoporosis

To obtain the compressive load bearing and energy absorption capacity of lumbar vertebrae of osteoporotic elderly for the everyday medical praxis in terms of the simple diagnostic data, like computed tomography (CT), densitometry, age, and sex. Compressive test of 54 osteoporotic cadaver vertebrae L1 and L2, 16 males and 38 females (age range 43-93, mean age 71.6 ± 13.3 years, mean bone mineral density (BMD) 0.377 ± 0.089 g/cm(2), mean T-score -5.57 ± 0.79, Z-score -4.05 ± 0.77) was investigated. Based on the load-displacement diagrams and the measured geometrical parameters of vertebral bodies, proportional, ultimate and yield stresses and strains, Young's modulus, ductility and energy absorption capacity were determined. Three vertebral regions were distinguished: superior, central and inferior regions, but certain parameters were calculated for the upper/ lower intermediate layers, as well. Cross-sectional areas, and certain bone tissue parameters were determined by image analysis of CT pictures of vertebrae. Sex- and age-related decline functions and trends of strength characteristics were determined. Size-corrected failure load was 15%-25% smaller in women, proportional and ultimate stresses were about 30%-35% smaller for women in any region, and 20%-25% higher in central regions for both sexes. Young's moduli were about 30% smaller in women in any region, and 20%-25% smaller in the central region for both sexes. Small strains were higher in males, large strains were higher in females, namely, proportional strains were about 25% larger in men, yield and ultimate strains were quasi equal for sexes, break strains were 10% higher in women. Ultimate energy absorption capacity was 10%-20% higher in men; the final ductile energy absorption capacity was quasi equal for sexes in all levels. Age-dependence was stronger for men, mainly in central regions (ultimate load, male: r = -0.66, p < 0.01, female: r = -0.52, p < 0.005; ultimate stress, male: r = -0.69, p < 0.01, female: r = -0.50, p < 0.005; Young's modulus, male: r = -0.55, p < 0.05, female: r = -0.52, p < 0.005, ultimate stiffness, male: r = -0.58, p < 0.05, female: r = -0.35, p < 0.03, central ultimate absorbed energy density, male: r = -0.59, p < 0.015, female: r = -0.29, p < 0.08). For the strongly osteoporotic population (BMD < 0.4 g/cm(2), T-score < -4) the statical variables (loads, stresses) showed significant correlation; mixed variables (stiffness, Young's modulus, energy) showed moderate correlation; kinematical variables (displacements, strains) showed no correlation with age. The strong correlation of men between BMD and aging (r = -0.82, p < 0.001) and betwen BMD and strength parameters (r = 0.8-0.9, p < 0.001) indicated linear trends in age-related strength loss for men; however, the moderate correlation of women between BMD and aging (r = -0.47, p < 0.005) and between BMD and strength parameters (r = 0.4-0.5, p < 0.005) suggested the need of nonlinear (quadratic) approximation that provided the better fit in age-related strength functions of females modelling postmenopausal disproportionalities.

Collapse of Reinforced Concrete Column by Vehicle Impact

Abstract: Walk‐up flats are typically supported by slender columns on the ground floor forming a soft storey. The column slenderness ratio can be in the order of 6–9. Some of these buildings are right next to busy streets and hence continuously exposed to the potential hazard of a vehicle impacting on a column in an accident. In the early part of this study, the ultimate energy absorption capacity of a reinforced concrete column is compared to the kinetic energy embodied in the moving vehicle. The energy‐absorption capacity is calculated from the force‐displacement curve of the column as determined from a nonlinear static (push‐over) analysis. The ultimate displacement of the column is defined at the point when the column fails to continue carrying the full gravitational loading. Results obtained from the nonlinear static analysis have been evaluated by computer simulations of the dynamic behavior of the column following the impact. Limitations in the static analysis procedure have been demonstrated. The effects of strain rate have been discussed and the sensitivity of the result to changes in the velocity function and stiffness of the impacting vehicle has also been studied.

Influence of hysteretic dampers on the seismic response of reinforced concrete wide beam–column connections

This research investigates the seismic performance up to collapse, and the ultimate energy absorption capacity of, existing nonductile reinforced concrete frames with wide beam–column connections seismic upgraded with brace-type hysteretic dampers. Four 2/3 scale exterior and interior connections with and without brace dampers were constructed and tested in a shaking table. The hysteretic dampers were designed so as to increase the lateral stiffness of the connection by ten times, and to limit the maximum interstory drift below 0.7% of the story height. The test models were subjected to a series of seismic simulations of increasing peak ground acceleration until collapse. The brace dampers reduced the maximum interstory drifts by 60%–80%, and increased the ultimate energy dissipation capacity of the exterior and interior connections by 12 and 4 times respectively. The RC elements of the connections equipped with brace dampers remained in nearly elastic conditions (i.e. with minor damage) until one of the brace dampers failed.

Stability and ductility of steel structures under cyclic loading

MATERIAL PROPERTIES AND PLASTICITY MODELS: The Experimental Basis of Material Constitutive Laws of Structural Steel under Cyclic and Nonproportional Loading (G.C. Lee, K.C. Chang, and K. Sugiura). Instability of Steel Short Column under Cyclic Loadings (K. Sugiura, E. Watanabe, G.C. Lee, and K.C. Chang). Bounding Surface Plasticity Model for Steel under Cyclic Loading (Y.F. Dafalias). A Uniaxial Stress-Strain Model for Structural Steels under Cyclic Loading (E. Mizuno, C. Shen, Y. Tanaka, and T. Usami). High Performance Steels for Earthquake Resistant Building Structure in Japan (H. Kuwamura). Experimental Observations: Cyclic Behavior of Gusset Plate Connections in V-Braced Steel Frames (A. Astaneh). Cyclic Post-Buckling Behavior of Steel Bracing Members (S.C. Goel). Cyclic Local Buckling of EBF Shear Links with or without Axial Force (K. Kasai and E.P. Popov). Stability of Beams in Eccentrically Braced Frames (M.D. Engelhardt, K.C. Tsai, and E.P. Popov). Buckling and Fracture in Cyclically Loaded Truss Girders (C.C. Chen and L.W. Lu). Steel and Concrete-Filled Steel Compression Members under Cyclic Loading (T. Usami, S. Mizutani, T. Aoki, and Y. Itoh). Ductility and Ultimate Strength of Concrete-Filled Steel Members (T. Kitada). Ductility of Steel Bridge Piers from Dynamic Loading Tests (K. Kawashima, G.A. MacRae, K. Hasegawa, T. Ikeuchi, and K. Oshima). Experimental Investigation on Hysteretic Behavior of Thin-Walled Box Beam-to-Column Connections (N. Nishimura, W.S. Hwang, and Y. Fukumoto). Experiments on Partially Encased Composite Columns (K. Takanashi and A.S. Elnashai). Substructured Hybrid Earthquake Loading Test of Steel Box Pier Models (Y. Yamada, H. Iemura, W. Tanzo, M. Yasuda, and S. Oka). Analytical Modeling: Numerical Experiment on Buckling/Plastic Collapse Behavior of Plates under Cyclic Loading (T. Yao and P.I. Nikolov). Multi-Spring Joint Model for Inelastic Behavior of Steel Members with Local Buckling (K. Ohi and K. Takanashi). Modelling of Hysteretic Behavior of Thin-Walled Box Members (E. Watanabe , K. Sugiura, T. Mori, and I. Suzuki). Prediction of Damage and Residual Strength of Tubular Member under Collision (H. Murakawa, Y. Ueda, and D. Xiang). Toward a Mythology of Cyclic Lateral Buckling of Beams (K.D. Hjelmstad). Cyclic Plastic Collapse of Steel Planar Frames (K. Uetani). Ultimate Energy Absorption Capacity of Moment Frames under Earthquakes (H. Akiyama). Design Implementation: Width-to-Thickness Ratios for Plate Elements in Earthquake Engineering Design of Steel Structures (Y. Fukumoto and Y. Itoh). Earthquake Resistant Design of Ductile Braced Steel Structures (S.C. Goel). Analysis and Design of Steel Braces and Braced Frames in Building Structures (M. Nakashima and M. Wakabayashi). Seismic Resistant Design of Steel Moment Resisting Frames Considering Panel-Zone Deformations (W. F. Chen and J.Y.R. Liew). Estimation of the Deformation Capacity of Steel Bridge Piers (G.A. MacRae and K. Kawashima). Future Research Needs. Future Research Needs (T.V. Galambos). Appendix A - The State of the Art: Ductility and Cyclic Buckling - A Japanese Contribution in the Field of Civil Engineering (E. Watanabe and M. Dogaki). Appendix B - Seminar Attendees. Author Index.