| Report # | 26 |
| Report Date | 06-05-2002 |
| Country | IRAN |
| Housing Type | Steel Moment Frame Building |
| Housing Sub-Type | Steel Moment Frame Building : Brick masonry infills |
|
Author(s)
|
Behrokh H. Hashemi, Mohsen G. Ashtiany |
|
Reviewer(s)
|
Farzad Naeim |
Important
This encyclopedia contains information contributed by various earthquake engineering professionals around the world. All opinions, findings, conclusions & recommendations expressed herein are those of the various participants, and do not necessarily reflect the views of the Earthquake Engineering Research Institute, the International Association for Earthquake Engineering, the Engineering Information Foundation, John A. Martin & Associates, Inc. or the participants' organizations.
Summary
This housing type is commonly used for low-rise building construction in Iran, mainly for family apartment buildings. This structure is characterized with a special type of semi-rigid beam-to-column connection called "Khorjinee connection." This connection consists of a pair of continuous beams spanning over several columns and connected to the column sides by means of angle sections. Beam and column are welded to the angle section. A major problem with the Khorjinee connection is that it is very difficult to improve the rigidity of the connection in the weak direction (the direction perpendicular to the connection) since the crossed beams are connected to the web of Khorjinee beams. Thus, in the weak direction of the frames, the connections are considered as pinned (hinges) and the bracing is used to resist seismic loads. However, in the Khorjinee direction, since the possibility of using the bracing is very limited, the frame is considered a rigid structure. Also,
out-of-plane partial beam-to-column transfer of bending moment and early onset of failure in the angles are the most likely causes of failure for a building subjected to lateral earthquake loads. These buildings are vulnerable in earthquakes (e.g., 1990 Manjil earthquake).
1. General Information
Buildings of this construction type can be found in This type of construction is used all over the urban and in some rural areas of Iran, especially in less humid regions. The percentage of this housing type in those regions is almost 70% of steel buildings. This type of housing construction is commonly found in both rural and urban areas. This construction type has been in practice for less than 100 years.
Currently, this type of construction is being built. This type of construction is followed in the last 30 years.
Figure 1: Typical Building
| 
Figure 2A: A typical layout of a Khorjinee connection | 
Figure 2B: An Illustration of a building with a Khorjinee connection |
|
2. Architectural Aspects2.1 Siting
These buildings are typically found in flat terrain. They do no share common walls with adjacent buildings. When separated from adjacent buildings, the typical distance from a neighboring building is several meters.
2.2 Building Configuration
The typical shape of a building plan for this housing type is rectangular. To view outside the building, typically a large window opening is in the transverse direction of the building.
This window almost takes 70% of the external wall area. The other wall has one or two doors or windows opening. The door sizes are typically 90 X 210 (cm) and the other window sizes are 160 X 90 (cm). The overall window and door areas are about 35% of the overall wall surface area.
2.3 Functional Planning
The main function of this building typology is multi-family housing. In a typical building of this type, there are no elevators and 1-2 fire-protected exit staircases.
2.4 Modification to Building
Figure 3: Plan of a Typical Building
|
3. Structural Details3.1 Structural System
| Material | Type of Load-Bearing Structure | # | Subtypes | Most appropriate type |
| Masonry | Stone Masonry
Walls | 1 | Rubble stone (field stone) in mud/lime
mortar or without mortar (usually with
timber roof) | ☐ |
| 2 | Dressed stone masonry (in
lime/cement mortar) | ☐ |
| Adobe/ Earthen Walls | 3 | Mud walls | ☐ |
| 4 | Mud walls with horizontal wood elements | ☐ |
| 5 | Adobe block walls | ☐ |
| 6 | Rammed earth/Pise construction | ☐ |
Unreinforced masonry
walls | 7 | Brick masonry in mud/lime
mortar | ☐ |
| 8 | Brick masonry in mud/lime
mortar with vertical posts | ☐ |
| 9 | Brick masonry in lime/cement
mortar | ☐ |
| 10 | Concrete block masonry in
cement mortar | ☐ |
| Confined masonry | 11 | Clay brick/tile masonry, with
wooden posts and beams | ☐ |
| 12 | Clay brick masonry, with
concrete posts/tie columns
and beams | ☐ |
| 13 | Concrete blocks, tie columns
and beams | ☐ |
| Reinforced masonry | 14 | Stone masonry in cement
mortar | ☐ |
| 15 | Clay brick masonry in cement
mortar | ☐ |
| 16 | Concrete block masonry in
cement mortar | ☐ |
| Structural concrete | Moment resisting
frame | 17 | Flat slab structure | ☐ |
| 18 | Designed for gravity loads
only, with URM infill walls | ☐ |
| 19 | Designed for seismic effects,
with URM infill walls | ☐ |
| 20 | Designed for seismic effects,
with structural infill walls | ☐ |
| 21 | Dual system – Frame with
shear wall | ☐ |
| Structural wall | 22 | Moment frame with in-situ
shear walls | ☐ |
| 23 | Moment frame with precast
shear walls | ☐ |
| Precast concrete | 24 | Moment frame | ☐ |
| 25 | Prestressed moment frame
with shear walls | ☐ |
| 26 | Large panel precast walls | ☐ |
| 27 | Shear wall structure with
walls cast-in-situ | ☐ |
| 28 | Shear wall structure with
precast wall panel structure | ☐ |
| Steel | Moment-resisting
frame | 29 | With brick masonry partitions | ☑ |
| 30 | With cast in-situ concrete
walls | ☐ |
| 31 | With lightweight partitions | ☐ |
| Braced frame | 32 | Concentric connections in all
panels | ☐ |
| 33 | Eccentric connections in a
few panels | ☐ |
| Structural wall | 34 | Bolted plate | ☐ |
| 35 | Welded plate | ☐ |
| Timber | Load-bearing timber
frame | 36 | Thatch | ☐ |
| 37 | Walls with bamboo/reed mesh
and post (Wattle and Daub) | ☐ |
| 38 | Masonry with horizontal
beams/planks at intermediate
levels | ☐ |
| 39 | Post and beam frame (no
special connections) | ☐ |
| 40 | Wood frame (with special
connections) | ☐ |
| 41 | Stud-wall frame with
plywood/gypsum board
sheathing | ☐ |
| 42 | Wooden panel walls | ☐ |
| Other | Seismic protection systems | 43 | Building protected with base-isolation systems | ☐ |
| 44 | Building protected with
seismic dampers | ☐ |
| Hybrid systems | 45 | other (described below) | ☐ |
3.2 Gravity Load-Resisting System
The vertical load-resisting system is steel braced frame. Gravity loads are sustained by steel frames.
3.3 Lateral Load-Resisting System
The lateral load-resisting system is steel braced frame. In both directions of the building the lateral load-resisting system should be provided by steel bracing (according to seismic code of Iran). However in most of these buildings, the steel bracing system is only used in one direction (the direction which is perpendicular to the street). The other direction (which is usually parallel to street), due to the existence of large opening in the wall of this direction, does not have any lateral resisting system.
3.4 Building Dimensions
The typical plan dimensions of these buildings are: lengths between 20 and 20 meters, and widths between 15 and 15 meters. The building has 4 to 6 storey(s). The typical span of the roofing/flooring system is 4.5 meters. Typical Plan Dimensions: Length variation is 12 - 20 meters, width variation is 9 - 15 meters.
Typical Span: Usually span is 3 - 4.5 meters. The typical storey height in such buildings is 2.7 meters. The typical structural wall density is none. 0.1.
3.5 Floor and Roof System
| Material | Description of floor/roof system | Most appropriate floor | Most appropriate roof |
| Masonry | Vaulted | ☐ | ☐ |
Composite system of concrete joists and
masonry panels | ☐ | ☐ |
| Structural concrete | Solid slabs (cast-in-place) | ☐ | ☐ |
| Waffle slabs (cast-in-place) | ☐ | ☐ |
| Flat slabs (cast-in-place) | ☐ | ☐ |
| Precast joist system | ☐ | ☐ |
| Hollow core slab (precast) | ☐ | ☐ |
| Solid slabs (precast) | ☐ | ☐ |
Beams and planks (precast) with concrete
topping (cast-in-situ) | ☐ | ☐ |
| Slabs (post-tensioned) | ☐ | ☐ |
| Steel | Composite steel deck with concrete slab
(cast-in-situ) | ☐ | ☐ |
| Timber | Rammed earth with ballast and concrete or
plaster finishing | ☐ | ☐ |
| Wood planks or beams with ballast and concrete or plaster finishing | ☐ | ☐ |
| Thatched roof supported on wood purlins | ☐ | ☐ |
| Wood shingle roof | ☐ | ☐ |
| Wood planks or beams that support clay tiles | ☐ | ☐ |
Wood planks or beams supporting natural
stones slates | ☐ | ☐ |
Wood planks or beams that support slate,
metal, asbestos-cement or plastic corrugated
sheets or tiles | ☐ | ☐ |
Wood plank, plywood or manufactured wood
panels on joists supported by beams or walls | ☐ | ☐ |
| Other | Described below | ☑ | ☑ |
Concrete joists with infilled hollow blocks topped with concrete slab. Concrete joists with infilled hollow blocks topped with concrete slab
The floor and roof are considered to be rigid diaphragm.
3.6 Foundation
| Type | Description | Most appropriate type |
| Shallow foundation | Wall or column embedded in
soil, without footing | ☐ |
Rubble stone, fieldstone
isolated footing | ☐ |
Rubble stone, fieldstone strip
footing | ☐ |
Reinforced-concrete isolated
footing | ☑ |
Reinforced-concrete strip
footing | ☑ |
| Mat foundation | ☐ |
| No foundation | ☐ |
| Deep foundation | Reinforced-concrete bearing
piles | ☐ |
Reinforced-concrete skin
friction piles | ☐ |
| Steel bearing piles | ☐ |
| Steel skin friction piles | ☐ |
| Wood piles | ☐ |
| Cast-in-place concrete piers | ☐ |
| Caissons | ☐ |
| Other | Described below | ☐ |
Figure 4A: A typical floor slab construction
| 
Figure 4B: Critical Structural Details
| 
Figure 5A: A seismic deficiency: wrong connection detail |
Figure 5B: Seismic deficiency-use of undefined bracing system |
4. Socio-Economic Aspects4.1 Number of Housing Units and Inhabitants
Each building typically has 1 housing unit(s). 8 units in each building.
Typically there are from 4 to 8 units in building. The number of inhabitants in a building during the day or business hours is less than 5. The number of inhabitants during the evening and night is less than 5.
4.2 Patterns of Occupancy
One family usually occupies each housing unit.
4.3 Economic Level of Inhabitants
| Income class | Most appropriate type |
| a) very low-income class (very poor) | ☐ |
| b) low-income class (poor) | ☑ |
| c) middle-income class | ☑ |
| d) high-income class (rich) | ☐ |
Economic Level:
For Poor Class the Housing Price unit is 12500 and the Annual Income is 1000.
For Middle Class the Housing Price unit is 25000 and the Annual Income is 3000.
| Ratio of housing unit price to annual income | Most appropriate type |
| 5:1 or worse | ☑ |
| 4:1 | ☐ |
| 3:1 | ☐ |
| 1:1 or better | ☐ |
What is a typical source of
financing for buildings of this
type? | Most appropriate type |
| Owner financed | ☑ |
| Personal savings | ☑ |
Informal network: friends and
relatives | ☐ |
Small lending institutions / micro-
finance institutions | ☐ |
| Commercial banks/mortgages | ☑ |
| Employers | ☐ |
| Investment pools | ☐ |
| Government-owned housing | ☐ |
| Combination (explain below) | ☐ |
| other (explain below) | ☐ |
In each housing unit, there are 1 bathroom(s) without toilet(s), 1 toilet(s) only and no bathroom(s) including toilet(s).
Depending on the size of house, typically one or two bathrooms and one or two
latrines for each housing unit are built. .
4.4 Ownership
The type of ownership or occupancy is renting, outright ownership and ownership with debt (mortgage or other).
Type of ownership or
occupancy? | Most appropriate type |
| Renting | ☑ |
| outright ownership | ☑ |
Ownership with debt (mortgage
or other) | ☑ |
| Individual ownership | ☐ |
Ownership by a group or pool of
persons | ☐ |
| Long-term lease | ☐ |
| other (explain below) | ☐ |
5. Seismic Vulnerability5.1 Structural and Architectural Features
Structural/
Architectural
Feature | Statement | Most appropriate type |
| True | False | N/A |
| Lateral load path | The structure contains a complete load path for seismic
force effects from any horizontal direction that serves
to transfer inertial forces from the building to the
foundation. | ☐ | ☑ | ☐ |
Building
Configuration | The building is regular with regards to both the plan
and the elevation. | ☑ | ☐ | ☐ |
| Roof construction | The roof diaphragm is considered to be rigid and it is
expected that the roof structure will maintain its
integrity, i.e. shape and form, during an earthquake of
intensity expected in this area. | ☑ | ☐ | ☐ |
| Floor construction | The floor diaphragm(s) are considered to be rigid and it
is expected that the floor structure(s) will maintain its
integrity during an earthquake of intensity expected in
this area. | ☑ | ☐ | ☐ |
Foundation
performance | There is no evidence of excessive foundation movement
(e.g. settlement) that would affect the integrity or
performance of the structure in an earthquake. | ☑ | ☐ | ☐ |
Wall and frame
structures-
redundancy | The number of lines of walls or frames in each principal
direction is greater than or equal to 2. | ☑ | ☐ | ☐ |
| Wall proportions | Height-to-thickness ratio of the shear walls at each floor level is:
Less than 25 (concrete walls);
Less than 30 (reinforced masonry walls);
Less than 13 (unreinforced masonry walls); | ☐ | ☐ | ☑ |
Foundation-wall
connection | Vertical load-bearing elements (columns, walls)
are attached to the foundations; concrete
columns and walls are doweled into the
foundation. | ☑ | ☐ | ☐ |
Wall-roof
connections | Exterior walls are anchored for out-of-plane seismic
effects at each diaphragm level with metal anchors or
straps | ☐ | ☑ | ☐ |
| Wall openings | The total width of door and window openings in a wall
is:
For brick masonry construction in cement mortar : less
than ½ of the distance between the adjacent cross
walls;
For adobe masonry, stone masonry and brick masonry
in mud mortar: less than 1/3 of the distance between
the adjacent cross
walls;
For precast concrete wall structures: less than 3/4 of
the length of a perimeter wall. | ☐ | ☐ | ☑ |
| Quality of building materials | Quality of building materials is considered to be
adequate per the requirements of national codes and
standards (an estimate). | ☑ | ☐ | ☐ |
| Quality of workmanship | Quality of workmanship (based on visual inspection of
few typical buildings) is considered to be good (per
local construction standards). | ☐ | ☑ | ☐ |
| Maintenance | Buildings of this type are generally well maintained and there
are no visible signs of deterioration of building
elements (concrete, steel, timber) | ☐ | ☑ | ☐ |
| Other | | ☐ | ☑ | ☐ |
5.2 Seismic Features
| Structural Element | Seismic Deficiency | Earthquake Resilient Features | Earthquake Damage Patterns |
| Wall | Due to lack of proper connections between walls and column, beam floor, walls are very vulnerable to seismic forces. | | |
| Frame (columns, beams) | Tear of the beam-to-column connections. | | |
| Roof and floors | None. | | |
| | | |
5.3 Overall Seismic Vulnerability Rating
The overall rating of the seismic vulnerability of the housing type is D: MEDIUM-LOW VULNERABILITY (i.e., good seismic performance), the lower bound (i.e., the worst possible) is C: MEDIUM VULNERABILITY (i.e., moderate seismic performance), and the upper bound (i.e., the best possible) is E: LOW VULNERABILITY (i.e., very good seismic performance).
| Vulnerability | high | medium-high | medium | medium-low | low | very low |
| | very poor | poor | moderate | good | very good | excellent |
Vulnerability
Class | A | B | C | D | E | F |
| ☐ | ☐ | ☑ | ☐ | ☑ | ☐ |
5.4 History of Past Earthquakes
| Date | Epicenter, region | Magnitude | Max. Intensity |
| 1990 | Manjil | 7.6 | IX |
Figure 6A: Building damage in the 1990 Manjil earthquake-collapse caused by the connection failure | 
Figure 6B: Building damage in the 1990 Manjil earthquake-collapse caused by the connection failure | 
Figure 6C: Minor damage due to pounding between two adjacent buildings in the 1990 Manjil earthquake |
Figure 6D: Failure due to soft story behavior in the 1990 Manjil earthquake |
6. Construction6.1 Building Materials
| Structural element | Building material | Characteristic strength | Mix proportions/dimensions | Comments |
| Walls | Clay brick masonry Concrete Steel bars. | 100 kg/cm² 8 kg/cm² 210 kg/cm² 4200 kg/cm². | 1:6 / 55 X 110 X 220 (mm) 1:2:4 n/a. | |
| Foundation | | | | |
| Frames (beams & columns) | Steel. | 2400 kg/cm² | | |
| Roof and floor(s) | Concrete. | 210 kg/cm². | | |
6.2 Builder
It is typically built by developers or for speculation.
6.3 Construction Process, Problems and Phasing
Typically developers build these types of constructions. Process starts with the foundations and fixing base plates on them. Then erection of steel frame and placing of joists and blocks, purring the concrete topping and then working out the infill walls and finally putting the finishing on the hole building. The construction of this type of housing takes place incrementally over time. Typically, the building is originally designed for its final constructed size.
6.4 Design and Construction Expertise
As far as the member sizes and foundations design concern, engineers are expert enough to design this type of building. In most projects engineers do not address any detail of the connection and they leave this part of job to experienced builders. For design of building, engineers and architectures are both involved. However, in most projects, during the construction process they do not spend any remarkable time to visit the site.
6.5 Building Codes and Standards
This construction type is addressed by the codes/standards of the country. The first official issue about this type of building was in 1999. The Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard 2800) in its 2nd revised edition (1999) addressed this type of construction to be considered as a Type 2 construction (i.e. simple framing in both directions). Iranian Code of Practice for Seismic Resistant Design of Building, 2nd Edition-1999 Iranian National Building Code, Part: 10, Steel Structures, 1994.
The building department of municipalities approves the design and holds the designer responsible for the projects. After finishing the construction the municipal authorities check the finished project and issue occupancy permit stage. However, most of these controls are the subjects of the architectural views.
6.6 Building Permits and Development Control Rules
This type of construction is a non-engineered, and not authorized as per development control rules. Building permits are required to build this housing type.
6.7 Building Maintenance
Typically, the building of this housing type is maintained by Builder, Owner(s) and Tenant(s).
6.8 Construction Economics
For only load bearing system, the cost of this type of building is about 300,000-400,000 Rials/m² (150-200 $US/m²). For a typical 4 to 6 stories building needs about 30 to 45 days to complete the load bearing structure.
7. Insurance
Earthquake insurance for this construction type is typically available. For seismically strengthened existing buildings or new buildings incorporating seismically resilient features, an insurance premium discount or more complete coverage is unavailable. N/A.
8. Strengthening
8.1 Description of Seismic Strengthening Provisions
Strengthening of Existing Construction :
| Seismic Deficiency | Description of Seismic Strengthening provisions used |
| Steel frame | Add diagonal steel bracings as required (high cost/high effectiveness/simple construction) |
| Connections | Strengthening connections by adequate and proper welding (medium cost/medium effectiveness/simple construction) |
| Foundations | At the location of the new bracing, strengthening of foundation is essential (high cost/medium effectiveness/complex construction) |
Strengthening of New Construction :
| Seismic Deficiency | Description of Seismic Strengthening provisions used |
| Steel frame | Design steel frame for gravity load and steel bracing for lateral resistant system (medium cost/medium effectiveness) |
| Connections | Provide proper details for connections (low cost/high effectiveness) |
| Foundations | Proper design (low cost/high effectiveness) |
8.2 Seismic Strengthening Adopted
8.3 Construction and Performance of Seismic Strengthening
Figure 7A: Illustration of Seismic Strengthening Techniques-New Braces Added to the Main Frame | 
Figure 7B: Strengthening of the existing braces
| 
Figure 7C: Stiffener plates used for strengthening the connections |
Figure 7D: Detail used to join footing together through steel tie beam |
Reference(s)- Effect of Semi-Rigid "Khorjinee" Connections in Dynamic Response of Steel Structures
Tehranizadeh,M., Ghafory-Ashtiany,M., Maleki,M. and Tiv,M.
Eleventh World Conference on Earthquake Engineering. Paper No. 1737 1996
- Manjil-Rudbar Earthquake of June 20,90 Reconnaissance Report
IIEES Publication No. 70-91-1, Tehran, Iran 1991
- Iranian Code of Practice for Seismic Resistant Design of Building, 2nd Edition
Building and Housing Research Center, BHRC-PN S 253, Tehran, Iran 1999
- Iranian National Building Code, Part 10 Steel Structures
Ministry of Housing and Urban Development, Tehran, Iran 1994
- Seismic Strengthening of a ten story steel framed hospital
Nateghi-A.,F.
Proceedings of the Second International Conference on earthquake resistant construction and design. Berlin/ 15-17 June 1994 1994
- Retrofitting of Earthquake-Damaged Steel Buildings
Nateghi-A.,F.
J. Engineering Structures, Vol. 17, No. 10, pp. 749-755 1995
- Seismic Upgrade Design of a Low-rise Steel Buildings
Nateghi-A.,F.
J. Engineering Structures, Vol. 19, No. 11, pp. 954-963 1997
Author(s)- Behrokh H. Hashemi
Assistant Professor, IIEES
No. 27 Arghavan St. Dibaji Farmanieh, Tehran 19531, IRAN
Email:behrokh@iiees.ac.ir FAX: (98-21) 229-9479
- Mohsen G. Ashtiany
Professor/President, IIEES
No. 27 Arghavan Street Dibaji Farmanieh, Tehran 19531, IRAN
Email:ashtiany@dena.iiees.ac.ir FAX: (98-21) 229-9479
Reviewer(s)- Farzad Naeim
Vice President
, John A. Martin & Associates
Los Angeles CA 90015, USA
Email:farzad@johnmartin.com FAX: (213) 483-3084
