Seismic Performance Enhancement of Steel Knee-Braced Frames through Optimization of Knee Length and Supplemental Supports

Alaa T. Mohammed; Mohammad Hossein Adib Rad

doi:10.2478/cee-2027-0006

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Seismic Performance Enhancement of Steel Knee-Braced Frames through Optimization of Knee Length and Supplemental Supports

Civil and Environmental Engineering

AHEAD OF PRINT

By: Alaa T. Mohammed and Mohammad Hossein Adib Rad

Open Access

|Jul 2026

Figures & Tables

Uniaxial Stress-Strain Relationship for Steel Material

Experimental Test Setup Configuration (Zahrai & Jalali, 2014)

Analytical Model of Knee-Braced Frame with Component Identification (Zahrai & Jalali, 2014)

Experimental Hysteresis Loop Validation (Zahrai & Jalali, 2014)

Quasi-Static Cyclic Loading Protocol Following ATC-24 Guidelines

Validation of Hysteretic Response: Experimental versus Numerical Simulation

Finite Element Model of Enhanced KBF System: Mesh (Left); Geometry (Right)

von Mises Stress Distribution in KBF01-T Model

von Mises Stress Distribution in KBF02-T Model

von Mises Stress Distribution in KBF03-T Model

Hysteretic Response of KBF01-T Under Quasi-Static Cyclic Loading

Hysteretic Response of KBF02-T Under Quasi-Static Cyclic Loading

Hysteretic Response of KBF03-T Under Quasi-Static Cyclic Loading

Performance Degradation: Stiffness and Energy Dissipation Ratios

Proposed dual-phase knee-braced frame (KBF-N) system

Comparative Hysteresis Response: (Left) Conventional KBF02-T and (Right) Enhanced KBF02-N

Comparative Hysteresis Response: (Left) Conventional KBF01-T and (Right) Enhanced KBF01-N

Comparative Hysteresis Response: (Left) Conventional KBF03-T and (Right) Enhanced KBF03-N

Loading Configuration: Concentrated Load Application Points on Beam

Time-History Displacement Response: Enhanced vs. Conventional KBF Systems

Structural Performance Degradation: Stiffness and Energy Dissipation Ratios

SAMPLE	FORCE [TON]	RATIO [%]	ENERGY [KN.M]	RATIO [%]
KBF01-T	29	100	46.36	100
KBF02-T	22	77	20.53	44
KBF03-T	17	59	9.85	21

Gravitational Load Calculation

Materials	Mass per unit volume [Kgf/m³]	Thickness [m]	Unit weight of surface [kgf/m²]
Cement mosaic	2250	0.02	45
Sand-cement mortar	2100	0.03	63
Concrete slab	2500	0.05	125
Concrete beam	2500	2x(0.1x0.25)	125
Concrete block	-	-	100
Gypsum and soil	1600	0.02	32
White gypsum	1300	0.01	13
			503

Section Properties of Validation Model (Zahrai & Jalali, 2014)

Spec.

Web stiffeners

Knee

Brace

Beam

Column

Steel properties

Distance [mm]

Thickness [mm]

Length [mm]

Section

Length [mm]

Section

Length [mm]

Section

Length [mm]

Section

Fy [N/mm²]

Fu [N/mm²]

KBF 1

100

800

IPE140

4300

2UNP80

3600

IPE180

3500

2IPE140

333.9

482.7

Stiffness Enhancement in Conventional versus Novel KBF Systems

SAMPLE	FORCE [TON]	RATIO [%]
KBF01-T	31	13
KBF01-N	36	13
KBF02-T	32	20
KBF02-N	40	20
KBF03-T	25	26
KBF03-N	34	26

Geometric and Material Properties of Supplemental Supports in Enhanced KBF System

Sample	H [mm]	B [mm]	W [mm]	F [mm]	D [mm]	S [mm]	Fy [Mpa]	Fu [Mpa]
KNF01-N	188	92	6	17	7	260	333.9	482.7
KNF02-N	194	92	6	17	10	520	333.9	482.7
KNF03-N	194	92	6	17	10	690	333.9	482.7

Section Properties and Material Characteristics of Numerical Models

Sample	Knee Elem./ Length	Brace	Beam	Column	Fy [Mpa]	Fu [Mpa]	E [Mpa]
KBF01-T	IPE140 / 800mm	2UNP80	IPE180	2IPE140	333.9	482.7	210000
KBF02-T	IPE140 / 1400mm	2UNP80	IPE180	2IPE140	333.9	482.7	210000
KBF03-T	IPE140 / 1800mm	2UNP80	IPE180	2IPE140	333.9	482.7	210000

References

Authors

Metrics

Articles in this issue

DOI: https://doi.org/10.2478/cee-2027-0006 | Journal eISSN: 2199-6512 | Journal ISSN: 1336-5835

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Language: English

Submitted on: May 9, 2026

Accepted on: Jun 8, 2026

Published on: Jul 22, 2026

Published by: University of Žilina

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

Ductility Enhancement

Related subjects:

Business and economics,

Business management,

Industries,

Environmental management

© 2026 Alaa T. Mohammed, Mohammad Hossein Adib Rad, published by University of Žilina
This work is licensed under the Creative Commons Attribution 4.0 License.

AHEAD OF PRINT

Seismic Performance Enhancement of Steel Knee-Braced Frames through Optimization of Knee Length and Supplemental Supports

Figures & Tables

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Structural Performance Degradation: Stiffness and Energy Dissipation Ratios

Gravitational Load Calculation

Section Properties of Validation Model (Zahrai & Jalali, 2014)

Stiffness Enhancement in Conventional versus Novel KBF Systems

Geometric and Material Properties of Supplemental Supports in Enhanced KBF System

Section Properties and Material Characteristics of Numerical Models

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