Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Simplified mechanical models for the nonlinear dynamic analysis of elasto-plastic steel structures impacted by a rigid body
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Buildings subjected to impact and explosion are usually studied using large scale and highly nonlinear finite element model which are time-consuming. The first part of the thesis deals with the development of simple and accurate models for evaluating the nonlinear inelastic behaviour of steel frame structures subjected to impact. The research work in this part has produced four simplified models. The first model concerns with a 4DOF model that reproduces the behaviour of the impacted column. The restraining effect from the rest of the structure is modelled by an elastic spring, a head mass and a static load applied at the top of the column. In the second model, the impacted column is then further simplified using a SDOF model. The behaviour of the SDOF model is governed by an analytical force-displacement expressions of the column loaded by a located force. The maximum displacement of the impacted column can also be determined explicitly by adopting an energy-equivalent approach. Afterwards, in an effort to model the whole structure, two finite element models are developed. For these models, a co-rotational super-element that consists of a beam element and two generalized elasto-plastic hinges is obtained by performing a static condensation. An elastic flexible beam element is used in the first finite element model, whereas a rigid beam element is considered in the second one.

In these models, inelasticity is concentrated at generalized elasto-plastic hinges which are modelled by combined axial-rotational springs. The behaviour of the hinges is uncoupled in the elastic range while an axial-bending interaction is considered in the plastic range making it possible to reproduce a wide range of cross-sections and joints. In addition, unilateral contact between rigid point masses is considered and the energy loss during impact is accounted by means of a restitution coefficient following Newton’s impact law. Energy-momentum scheme is used to solve the equations of motion produced by these models.

The second part of the thesis concerns with the performance of the connectors in composite steel-concrete slabs under explosion. The purpose is to determine residual capacities of the shear connectors after being damaged by explosion using large-scale pull-out and push-out experimental tests and finite element simulations.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. , 176 p.
Series
TRITA-BKN. Bulletin, ISSN 1103-4270 ; 151
National Category
Building Technologies
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-217281OAI: oai:DiVA.org:kth-217281DiVA: diva2:1154960
Public defence
2017-12-08, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20171106

Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-07Bibliographically approved
List of papers
1. A simplified model for nonlinear dynamic analysis of steel column subjected to impact
Open this publication in new window or tab >>A simplified model for nonlinear dynamic analysis of steel column subjected to impact
2016 (English)In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 86, 37-54 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a new simplified model of the nonlinear dynamic behavior of a steel column subjected to impact loading. In this model, the impacted column, which undergoes large displacement, consists of two rigid bars connected by generalized elastic–plastic hinges where the deformation of the entire steel column as well as the connections is concentrated. The effect of the rest of the structure on the column is modeled by an elastic spring and a point masse both attached to the top end of the column which is also loaded by a compressive force. The plastification of the hinges follows the normality rule with a yield surface that accounts for the interaction between M and N. The latter is described by a super-elliptic yield surface that allows ones to consider a wide range of convex yield criterion by simply varying the roundness factor that affects the shape of the limit surface. By including these features, the model captures both geometry and material nonlinearities. Both the flow rule and the equations of motion are integrated using the midpoint scheme that conserves energy. The non-smooth nature of impact is considered by writing the equations of motion of colliding masses using differential measures. Contact conditions are written in terms of velocity and combined with Newton's law to provide the constitutive law describing interactions between masses during impact. Numerical applications show that the model is able to capture the behavior of a column subjected to impact.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Catenary action, Energy-conserving scheme, Generalized plastic hinges, Impact, Non-smooth mechanics, Progressive collapse, Steel structures, Control nonlinearities, Dynamic analysis, Hinges, Steel construction, Structural dynamics, Catenary actions, Energy-conserving, Plastic hinges, Equations of motion
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-195223 (URN)10.1016/j.ijnonlinmec.2016.07.005 (DOI)000386405200007 ()2-s2.0-84982145085 (Scopus ID)
Note

QC 20161117

Available from: 2016-11-17 Created: 2016-11-02 Last updated: 2017-11-06Bibliographically approved
2. An enhanced SDOF model to predit the behaviour of a steel column impacted by a rigid body
Open this publication in new window or tab >>An enhanced SDOF model to predit the behaviour of a steel column impacted by a rigid body
2017 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 152, 771-789 p.Article in journal (Refereed) Published
Abstract [en]

The transient dynamic response of a steel beam-column subjected to impact loading is a complex phenomenon involving large localized plastic deformations and non-smooth contact interactions. Exposed to high intensity of the contact force generated from impact, the beam-column may undergo large displacement and inelastic deformation. Previous research has shown that a calibrated elasto-plastic single degree of freedom system is able to reproduce both the displacement and the force time-history of a steel beam subjected to non-impulsive loading or low-velocity impact. In these models, the static force-displacement curve is derived from either experiments or detailed 3D nonlinear analysis. Tri-linear resistance function has been extensively used to reproduce the different stages of the response including catenary effects. A rigorous treatment of such a complex problem calls for the use of non-smooth analysis tools to handle the impulsive nature of the impact force, the unilateral constraint, the impenetrability condition and the discontinuity of the velocity in a rigorous manner. In this paper, we present a non-smooth elasto-plastic single degree of freedom model under impact loading that permits the use of arbitrary resistance function. Adopting the non-smooth framework offers tools such as differential measures and convex analysis concepts to deal with unilateral contact incorporating Newton’s impact law. The mid-point scheme is adopted to avoid numerical unrealistic energy decay or blowup. Furthermore, the non-penetration condition is numerically satisfied by imposing the constraint at only the velocity level to guarantee energy-momentum conservation [1]. The explicit expression of resistance functions of the beam that are used in the SDOF model are obtained from a simplified nonlinear static analysis of two beam-column models. In the analysis, a linear relation between normal force and bending moment is assumed for the plastification of the hinges. Two proposals to simplify the explicit expressions of the model’s response behavior are given. Performing an energy-based analysis, we predict maximum displacement that is needed to absorb the kinetic energy arising from the impact for different coefficient of restitution. The numerical examples underline the validity of the model by showing good agreement with the predictions of reference models.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
Single degree of freedom, Impact, Non-smooth analysis, Steel structures, Catenary action, Analytical solution
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-217277 (URN)10.1016/j.engstruct.2017.08.061 (DOI)
Note

QC 20171106

Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-06Bibliographically approved
3. Co-rotational planar beam element with generalized elasto-plastic hinges
Open this publication in new window or tab >>Co-rotational planar beam element with generalized elasto-plastic hinges
Show others...
2017 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 151, 188-205 p.Article in journal (Refereed) Published
Abstract [en]

Slender elements in framed structures may undergo large displacement and experience highly nonlinear behavior. This paper presents a two-node co-rotational flexible beam with generalized elasto-plastic hinges at the beam ends. A Condensation procedure is used to remove the internal degrees of freedom so that the formulation is easily incorporated with the standard co-rotational approach. A family of asymmetric and convex yield surfaces of super-elliptic shape is considered for the plastic behavior of the hinges. By varying the roundness factor, an infinite number of yield surfaces are obtained making it possible to select the yield function that best fit experimental data of any type of cross-section and material. The nonlinear response of bolted connections subjected to both bending and axial forces are conveniently modeled with such a yield surface. Discrete constitutive equations for the hinge plastic deformations are derived using the implicit scheme for both smooth and non-smooth cases. Numerical examples demonstrate the accuracy of the model in predicting the large displacement inelastic response of framed structures. Effect of the roundness factor on the ultimate load strongly depends on the structure typology. It was observed that cyclic loading produces pinching effect, cyclic softening and ductile behavior. Those effects are more pronounced with anisotropic yield criteria.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
Steel structure, Nonlinear analysis, Generalized plastic hinge, Co-rotational approach, Large displacement, Super-elliptic yield criterion
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-217278 (URN)10.1016/j.engstruct.2017.07.085 (DOI)000412960600015 ()2-s2.0-85028705221 (Scopus ID)
Note

QC 20171106

Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-06Bibliographically approved
4. Co-rotating rigid beam with generalized plastic hinges for the nonlinear dynamic analysis of planar framed structures subjected to impact loading
Open this publication in new window or tab >>Co-rotating rigid beam with generalized plastic hinges for the nonlinear dynamic analysis of planar framed structures subjected to impact loading
2017 (English)In: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925Article in journal (Refereed) Submitted
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-217279 (URN)
Note

QC 20171106

Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-06Bibliographically approved
5. Residual stiffness and strength of shear connectors in steel-concrete composite beams after being subjected to a pull-out pre-damaging: An experimental investigation
Open this publication in new window or tab >>Residual stiffness and strength of shear connectors in steel-concrete composite beams after being subjected to a pull-out pre-damaging: An experimental investigation
Show others...
2017 (English)In: Structures, ISSN 2352-0124, Vol. 11, 189-205 p.Article in journal (Refereed) Published
Abstract [en]

Horizontal stability of the medium rise steel frame structures is usually ensured by vertical bracings and diaphragm action of composite floors. Load transfer within the composite floor system is made through shear connectors, e.g. headed studs. In an event of explosion, such connectors must reserve sufficient residual stiffness and strength in order to avoid a sudden or delayed collapse of the building. These remaining capacities have not been experimentally studied yet in the literature. This paper presents large scale horizontal push out tests to determine the residual stiffness of the shear connectors after being initially damaged by explosion. The initial damaging is reproduced by a pull-out test using a quasi-static loading. Two types of numerical simulation have also been developed using ABAQUS/CAE software to provide a better understanding of the experimental results.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
Composite floor, Explosion, Profile steel sheet, Pullout, Push-out, Residual strength, Shear stud
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-209865 (URN)10.1016/j.istruc.2017.05.003 (DOI)2-s2.0-85020418866 (Scopus ID)
Note

QC 20170627

Available from: 2017-06-27 Created: 2017-06-27 Last updated: 2017-11-06Bibliographically approved

Open Access in DiVA

fulltext(2057 kB)27 downloads
File information
File name FULLTEXT01.pdfFile size 2057 kBChecksum SHA-512
447af6451d58b5508bc9bce3d0fbf3572acca3bcaf8008c037ed93707d13ac58a9100aaeb939abc01236041c08f5f280f12f3dc83305f5fc6d60bb9fc3848abd
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Heng, Piseth
By organisation
Structural Engineering and Bridges
Building Technologies

Search outside of DiVA

GoogleGoogle Scholar
Total: 27 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 413 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf