Structural Engineering

Construction Engineering

Parking Planning and Design

PhiladelphiaNew York

WWW.HARMANGROUP.COM

Structural Engineering

PRESENTED BY

Tuna Yelkikanat, PE, LEED GA

Senior Associate / NY Office Director

Structural Renovation of Existing Buildings:Opportunities and Challenges

Lea Cosenza

Associate / Project Manager

NEW YORK | PHILADELPHIA

This presentation is eligible for 1 AIA Learning Unit

Topics of Discussion

• Structural renovation and repair/reinforcing steps

• Code analysis and lateral upgrades

• Vertical enlargements (Overbuilds)

• Early foundation, column and floor framing types

• Examples of structural damage

• Types of structural reinforcing techniques

Overview

Structural Renovation Steps

Study Documentation Available

Identify Type(s) of Construction

Identify Load Paths

Check for Visible Defects

Member(s), Connection(s), System(s)

Yes No

Structural Condition Assesment Report Code Analysis

Repairs Needed?

Structural Renovation Steps

Yes

Identify Repair Needs

Maintenance of

Structural Integrity

Unsafe Condition

Immediate Repairs

Make Repairs

Loads Lower or

Same As Original

Structural

Integrity Check

Certification of

Structure

No

Identify New Use and

New Live Loads

Loads Heavier

Than Original

Calculations for Actual

DL & LL as Required

Safety Factors

(Original or New?)

Reinforce Structure

as Required

• Referenced code; 2015 IEBC International Existing Building Code

• Local city codes and requirements on existing buildings (if applicable)

• Chapters 7 thru 8 on Alterations

• Chapter 11 on Additions/Enlargements

Code Analysis

• Types of Alterations

• Level 1 : Removal and replacement or the covering of existing materials,

elements, equipment or fixtures

• Level 2 : Reconfiguration of space, the addition or elimination of any door

or window, the reconfiguration or extension of any system, or the installation of any additional equipment

• Level 3 : Where the work area exceeds 50 percent of the building area

Code Analysis

• Level 1 Alterations : Structural provisions apply if replacement of equipment

and reroofing is planned. IBC governs unless;

• Additional dead load from roofing or equipment does not increase stress

on structural members by more than 5 percent

• Addition of second layer of roof covering weighing 3psf or less

• If reroofing more than 25% of the roof area for buildings assigned to

Seismic Design Category D, E or F, bracing of unreinforced masonry

parapets required to resist reduced seismic forces as specified in Section

301.1.4.2 of IEBC

• If roofing is removed from more than 50% of the roof area in high wind speed areas (Vult >115mph) roof diaphragms, their connections should

be evaluated based on IBC. If not capable to resist at least 75% of those

wind loads, strengthening is required.

Code Analysis

• Level 2 Alterations:

• New structural elements shall comply with IBC

• Existing structural elements supporting additional gravity loads shall

comply with IBC unless;

• Member stress is not increased by more than 5 percent

• Building is assigned to Group R occupancy with less than 5 dwelling

units, built with light frame construction methods

• Existing structural elements supporting additional lateral loads shall

comply with IBC wind loads and reduced seismic forces as specified in

Section 301.1.4.2 of IEBC unless;

• Demand capacity ratio of lateral elements are not increased by more

than 10 percent.

Code Analysis

• Level 3 Alterations

Same provisions for Level 2 apply plus;

• If more than 30% of the floor area proposed to be in structural alteration

next 5 years, evaluation of the lateral load resisting system is required

showing compliance with IBC wind loads and reduced seismic loads specified in IEBC

• If the building is assigned to Seismic Design Category F, evaluation of the

lateral load resisting system is required showing compliance with reduced

seismic loads specified in IEBC

• For buildings assigned to Seismic Design Category D, E or F with reinforced concrete or masonry walls with flexible roof diaphragms or

unreinforced masonry walls with any type of diaphragms, installation of

roof anchors at the roof line is required to resist reduced seismic loads

specified in IEBC

• Masonry parapets requires bracing for SDC C, D, E or F.

Code Analysis

• Additions

An addition to a building shall comply with IBC for new construction without

existing building to comply with any requirements unless addition impacts

existing building

• Existing structural elements supporting additional gravity loads and snow drift loads shall comply with IBC unless;

• Member stress is not increased by more than 5 percent

• Building is assigned to Group R occupancy with less than 5 dwelling

units, built with light frame construction methods

• Existing structural elements supporting additional lateral loads shall comply with IBC wind loads and reduced seismic forces as specified in

Section 301.1.4.2 of IEBC unless;

• Demand capacity ratio of lateral elements are nor increased by more

than 10 percent.

Code Analysis

Tips

• Review existing framing using LRFD design (Can often get 10% more load

capacity from a structure using LRFD vs. ASD)

• LRFD (Load and Resistance Factor Design)

• ASD (Allowable Strength Design)

• Test existing steel to determine if actual yield strength > yield strength used in original design

• Test existing concrete to determine if actual compressive strength >

compressive strength used in original design

• For vertical enlargement projects we might be able to find ways carrying

additional loads down to foundations without a need to reinforce existing foundations (E.g. introduction of a new stair or elevator tower)

Vertical Enlargements (Overbuilds)

2040 Market St

Types

• Deck on composite joists and

load bearing cold formed steel

walls

• Structural steel – slab on metal

deck with steel columns and beams – with concrete shear

walls going down through the

existing building and up to the

new roof.

Vertical Enlargements (Overbuilds)

Timber Grillage,

Platform Foundations

Wood Timber Spread Footing

• Identified by reviewing

existing drawings (if

available) or by digging test

pits by existing

columns/walls

• Soil investigation with

borings are recommended if

additional loading is

considered

• Material testing might be necessary

Stone Footings

Brick Footings

Early Foundation Types

Inverted Arch Foundations

Early Foundation Types

Beton Foundations

Concrete-like mixture of stone, rubble and mortar

Piles, grillage and platform with

stone or beton foundation platform

Early Foundation Types

Cast Iron Column Shapes

• Cast iron columns are typical.

Welding to cast iron columns is not

recommended. They are usually

round and can be easily identified by

survey.

• Some columns are made up of built

up plates and angles connected with

rivets to form W, H or Box shapes

• Fireproofing techniques such as

terracotta encasements are common

Built up column shapes (mostly riveted)

Early Column Types

Terra Cotta Encasements for Columns (Fireproofing)

Early Column Types

• Floors are typically draped mesh

concrete slab with cinder fill on top

• Concrete encasement of the beams

provide fireproofing

• Terracota arch floors are also common. They can be segmented or

flat arches. Floor beams are usually

wrought iron. Welding might be an

issue.

• Coupon testing is recommended whenever we load existing beams to

identify grade of the beam

Draped-Mesh Concrete Slab

Early Floor Systems

Terra Cotta Flat Arch FloorSegmental Terra Cotta Arch Floor

Early Floor Systems

Examples of Structural Damage

Corroded steel columns in brick

foundation walls

• Columns are embed in brick

foundation walls therefore suffered

water damage over the years

• Bad design. Columns should ideally

be supported on brick piers right

above the basement level

• We had to demo the brick around the

existing columns, do proper surface cleaning, well steel plates(tabs) on

the column and encase them in

concrete.

Examples of Structural Damage

Damaged flat brick arch floors

• Previous tenants created floor

openings at brick floors

• Floors had to be repaired or replaced

partially

• Steel rods tying wrought iron steel

beams together to take thrust force

Cast Iron: Casted in forms, not

weldable, very brittle material

Wrought Iron: Rolled shapes, had to be

tested to identify if welding is possible

Examples of Structural Damage

Load bearing brick wall damaged with

moisture

• Brick wall was deteriorated due to water

• Owner intended to hide the wall without

realizing it was a structural wall (before our involvement)

• We had to design a new load bearing wall

in front of the existing wall

Examples of Structural Damage

Missing floor

• Floor was removed during a previous

renovation

• Columns tied with steel rods that were

intended to brace columns

• Cast iron columns, not easy to tie new

steel members to them

• Picking up 5 stories above

• Owner decided to demo and rebuild new

• We can increase capacity of columns by welding angles and ignoring rivets.

Hollow cast iron columns can be filled with concrete.

• Beam capacity increase can be achieved by welding plates or WT/HSS

shapes to bottom flanges

• Cinder fill can be removed from flooring to reduce some weight, increase load capacity and gain some headroom

• Micro piles is an option to upgrade foundations

• New footings can be poured under brick footings (underpinning)

Structural Capacity Increase Techniques

2400 MARKET STREET

WWW.HARMANGROUP.COM

2400 Market - History

• Built around 1920’s

• Existing five story concrete automobile warehouse

• Two-way flat plate with circular concrete columns with capitals and drop panels

• Diagonal column grids

• Encompasses an entire city block

2400 Market – Overbuild

• New concrete cores on micropile supported mats

• Openings through existing floors

• Slip formed cores

• Sequence of construction

2400 Market – Shear Walls

2400 Market – Steel Overbuild

2400 Market – Steel Overbuild

2400 Market – Atrium

2400 Market - Promenade

2400 Market – Fitler Club

PRESENTED BY

Tuna Yelkikanat, PE, LEED GA

Senior Associate / NY Office Director

Structural Renovation of Existing Buildings:Opportunities and Challenges

Lea Cosenza

Associate / Project Manager

This presentation is eligible for 1 AIA Learning Unit

NEW YORK | PHILADELPHIA

Structural Engineering

Construction Engineering

Parking Planning and Design

PhiladelphiaNew York

WWW.HARMANGROUP.COM

Structural Engineering