International Workshop on Structural Concrete

Schedule of Events

7:00 am – 8:00 am WORKSHOP REGISTRATION Workshop attendees to pick up registration materials in the Exhibit Hall at ACI Registration

8:00 am – 8:15 am WELCOME REMARKS Moderated by Jack Moehle, Professor, University of California at Berkeley, former Chair of ACI 318

8:15 am – 9:45 am SESSION 1: CHANGES IN ACI 318-19, PART 1 OF 2 Moderated by James K. Wight, ACI Past President, Professor, University of Michigan

Presentation 1: New Shear Strength Equations and Modifications for Strut -and-Tie Method David Sanders, Professor and Department Chair, Iowa State University Presentation 2: New Development Length Requirements for Hooked and Headed Bars David Darwin, ACI Past President, Distinguished Professor and Department Chair, University of Kansas Presentation 3: Building Code Changes for Use of High-Strength Reinforcement

Dominic Kelly, Senior Principal, Simpson Gumpertz & Heger, Inc.

9:45 am – 10:15 am COFFEE BREAK

10:15 am – 12:00 pm SESSION 2: CONCRETE CONSTRUCTION IN THE MIDDLE EAST Moderated by Luke Snell, Concrete Consultant Presentation 1: Design, Qualification, Production, and Pumping of High -Strength, High-Performance Mass Concrete for Pile Cap of Dubai Creek Tower Fouad Yazbeck, Technical and Commercial Director, Universal Concrete Products – Unimix Presentation 2: Codes and Standards Used in the Middle East Mohamad Nagi, Director, Infrastructure Sustainability and Assessment Center, American University of Dubai; and Ahmed Shuraim, Chairman, Structural Committee, Saudi Arabia and Gulf Region Building Codes Presentation 3: Special Construction Considerations in the Middle East Charbel Aoun, Head of Consultancy Division, Advanced Construction Technology Services (ACTS)

12:00 pm – 1:30 pm INTERNATIONAL WORKSHOP LUNCH Introduction by David Lange, ACI Past President, Professor, University of Illinois Presentation: Infrastructure Projects in Qatar Related to 2022 World Cup Khaled Awad, ACI Past President, Chairman, Advanced Construction Technology (ACTS)

1:30 pm – 3:00 pm SESSION 3: DESIGN OF SUPER-TALL REINFORCED CONCRETE STRUCTURES

Moderated by Larry Novak, Chief Structural Engineer, International Code Council Presentation 1: Concrete Pushes Mexico to New Heights Roberto Stark, President, Stark & Ortiz, S.C. Presentation 2: Recent Supertall Concrete Towers in the Middle East Robert Sinn, Principal, Thornton Tomasetti; and John Peronto, Senior Principal, Thornton Tomasetti Presentation 3: Design Using High-Performance Concrete and Construction Method for Lotte World Tower in Seoul Edward Roberts, Senior Associate, LERA Consulting Structural Engineers

3:00 pm – 3:30 pm REFRESHMENT BREAK

3:30 pm – 5:00 pm SESSION 4: CHANGES IN ACI 318-19, PART 2 OF 2 Moderated by Jim Cagley, ACI Past President, Principal, Cagley & Associates, Inc.

Presentation 1: Design Verification Using Nonlinear Response History Analysis

Luis Garcia, ACI Past President, Professor (retired), Universidad de los Andes Presentation 2: New Seismic Provisions in Building Code

John Wallace, Professor, University of California at Los Angeles Presentation 3: Damage to Concrete Buildings with Precast Floors During the 2016 Kaikoura Earthquake Ken Elwood, Professor, University of Auckland

5:00 pm – 5:15 pm CLOSING REMARKS Moderated by Jack Moehle, Professor, University of California at Berkeley, former Chair of ACI 318; and James K. Wight, ACI Past President, Professor, University of Michigan

6:00 pm – 7:00 pm INTERNATIONAL WORKSHOP RECEPTION & YOUNG PRACTICING ENGINEER POSTER SESSION Hosted by Jack Moehle, Professor, University of California at Berkeley, former Chair of ACI 318

Session 1: Changes in ACI 318-19, Part 1 of 2 Moderated by James K. Wight, ACI Past President, Professor, University of Michigan

Papers in this session cover the most significant technical changes to design

requirements in the ACI 318-19 Building Code. Professor Sanders will discuss changes

to the Code equations for one-way shear in beams and slabs that have eliminated

many of the empirical shear strength equations. A “size-effect” term is now included

in the shear strength equations for members that do not have minimum transverse

reinforcement. Changes have also been made to the strut-and-tie definitions and

requirements. Professor Darwin will discuss modifications of tension development

lengths for straight, hooked, and headed bars. A broader range of steel and concrete

material strength were included in developing a database to support these required

changes. For hooked and headed bars, the development lengths will be a function of 1.5

bd and requirements for confinement reinforcement are increased. Structural

Engineer Dominic Kelly will discuss the acceptance of Grades 80 and 100 steel as

longitudinal and transverse reinforcement in most structural members. Primary use of high-strength steel will be

for design of columns and shear walls. Design requirements are not changed, but development lengths will be

increased.

Learning objectives:

1. Understand background and impact of new one-way shear strength equations for beams and slabs;

2. Understand modifications of tension development lengths for straight, hooked, and headed bars;

3. Understand potential impact of new confinement requirements for hooked and headed bars; and

4. Understand impact on design when using high-strength longitudinal and transverse steel.

Presentation 1—New Shear Strength Equations and Modifications for

Strut-and-Tie Method David Sanders, Professor and Department Chair, Iowa State University

Substantial changes have occurred in the one-way shear equations for reinforced

concrete. There is a single equation for all one-way shear capacity calculations in

reinforced concrete members. The changes address the issues of size effect in beams

and suspended slabs, and the impact of members without shear reinforcement and

low longitudinal reinforcement percentage. Under certain specified conditions, the

traditional equation based on 2√fc′ can still be used. There have been changes in the

strut-and-tie model definitions and requirements for struts, including removal of the

bottle-shaped strut. Additional checks are required for certain strut types without

minimum amounts of reinforcement.

Presentation 2—New Development Length Requirements for Hooked and Headed Bars David Darwin, ACI Past President, Distinguished Professor and Department Chair, University of Kansas

The new development length requirements in ACI 318-19 for hooked and headed bars are based on test results that include bar stresses at failure up to 153,000 psi (1055 MPa) and concrete compressive strengths up to 16,500 psi (114 MPa). Development lengths for hooked and headed bars are now functions of bar diameter to the 1.5 power and an approximation of concrete strength to the 1/4 power for compressive strengths below 6000 psi (41 MPa). The new provisions permit larger obstructions and closer spacing of headed bars than ACI 318-14. Requirements for cover, spacing, and confining reinforcement are redefined.

Presentation 3—Building Code Changes for Use of High-Strength

Reinforcement Dominic Kelly, Senior Principal, Simpson Gumpertz & Heger, Inc.

Because the 2011 edition of ACI 318 prohibited the use of Grade 80 reinforcement

for special seismic systems, bar producers have made much progress in how they

intend to produce high-strength reinforcement and researchers have completed

tests of members reinforced with high-strength bar and published their results and

recommendations. This progress and research along with information about bars

produced and research completed in other countries was sufficient for ACI

Committee 318 to consider allowing the use of high-strength reinforcement for

some applications. The result is that ACI 318-19 allows the use of Grade 100

reinforcement for many applications in which gravity loads are resisted, Grade 80

reinforcement for special moment frames, and Grade 100 reinforcement for

special structural walls. The ACI 318-19 changes allowing the use of high-strength reinforcement will be presented.

Session 2: Concrete Construction in the Middle East Moderated by Luke Snell, Concrete Consultant

Construction in the Middle East has many unique challenges. Many areas have

extreme high temperatures, low humidity, constant winds, and sulfates in the soils.

Areas near the Gulf and Red Seas have corrosion issues from the sea water.

This area has had a building boom and is home to some of the tallest buildings in the

world. These presentations will discuss how the challenges on construction in the

Middle East have been met and how the ACI 318 Code provides the guidance for

successful design and construction.

Learning objectives:

1. Understand how ACI 318 is applied to construction in the Middle East;

2. Learn the procedures for pumping concrete in extreme weather conditions;

3. Identify how construction techniques greatly vary in hot weather environments; and

4. Learn how environmental conditions influence design of concrete structures.

Presentation 1—Design, Qualification, Production, and Pumping of High-Strength, High-Performance Mass Concrete for Pile Cap of Dubai Creek Tower Fouad Yazbeck, Technical and Commercial Director, Universal Concrete Products – Unimix

The Tower at Dubai Creek Harbour, Dubai, is a stunning new tower design by Santiago Calatrava. The innovative design features a single concrete shaft laterally stabilized by an array of cables. This structural form results in a record-breaking point load that needs to be transferred from the bottom of the shaft to the barrette foundations. As a transfer structure, a circular, terrace-like structure has been designed requiring concrete strength of up to 100 MPa. Extraordinary teamwork between key stakeholders made it possible to achieve, 2 months ahead of schedule, the completion of Dubai Creek Tower Pile Cap. Four hundred and fifty skilled professionals, working day and night, managed to place 48,000 m3 of concrete in less than 9 months.

Presentation 2—Codes and Standards Used in the Middle East Mohamad Nagi, Director, Infrastructure Sustainability and Assessment Center, American University of Dubai; & Ahmed Shuraim, Chairman, Structural Committee, Saudi Arabia and Gulf Region Building Codes

The presentation highlights the following

topics with emphasis on Saudi Arabia and

the Gulf Cooperation Council (GCC): earlier

practices prior to 2001, overview of the

regional building code under the umbrella

of the Arab league, formation of the Saudi

National Committee for building code as a

milestone, first edition of the Saudi

Building Code, the Gulf building code, and

the 2018 Saudi Building code.

Presentation 3—Special Construction Considerations in the Middle East Charbel Aoun, Head of Consultancy Division, Advanced Construction Technology Services (ACTS)

Concrete construction in the Middle East present several challenges to the industry, starting by the demanding environmental conditions and spanning to the large-scale and fast-track construction demand. These challenges reflect several special considerations on the concrete practices. This presentation addresses these considerations in large-scale iconic projects across the Middle East. It takes as case studies two of the largest airport constructions in the region. This construction reached more than 6 million m3 of high-performance and colored concrete with a placing rate exceeding 15,000 m3 per day.

International Workshop Lunch Introduction by David Lange, ACI Past President, Professor, University of Illinois

David A. Lange, FACI, is Professor of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign, Urbana, IL. He joined the faculty of the Department of Civil and Environmental Engineering in 1992. He is Director of the Center of Excellence for Airport Technology, a research center working in partnership with the Chicago Department of Aviation and the O’Hare International Airport. A long-time ACI member, Lange served as ACI President in 2018-19, and continues service on the ACI Executive Board and ACI Board of Direction. His past positions include Chair of the ACI Technical Activities Committee, Chair of the Publications Committee, and Chair of the Board Outlook 2030 Task Group. He currently is a member of ACI Committees 236, Material Science of Concrete; 237, Self-Consolidating Concrete; 241, Nanotechnology of Concrete; and 544, Fiber-Reinforced Concrete. Lange received the ACI Wason Medal for Most Meritorious Paper in both 2003 and

2018. Lange is a Fellow of the American Ceramic Society and he received a J. William Fulbright Scholar Award in 2013. Lange served as Associate Department Head for Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign from 2004-2010. Lange earned his PhD in civil engineering from Northwestern University, an MBA from Wichita State University, and a BS in civil engineering from Valparaiso University.

Presentation—Infrastructure Projects in Qatar Related to 2022 World Cup Khaled Awad, ACI Past President, Chairman, Advanced Construction Technology (ACTS)

The state of Qatar won in 2010 the right to host the FIFA World Cup in 2022,

bringing this event to the Middle East for the first time. Qatar committed to build

eight stadiums along with a large infrastructure network to cope with the expected

influx of fans and tourists. The presentation will describe the works in the various

stadiums and infrastructure projects, and some of the unique technical challenges

they have faced.

Session 3: Design of Super-Tall Reinforced Concrete Structures Moderated by Larry Novak, Chief Structural Engineer, International Code Council

Concrete has become the structural engineers’ material of choice for high-rise

construction around the world. The majority of tall buildings constructed today

feature either primary structural systems using all reinforced concrete or a

composite system using a combination of reinforced concrete and structural steel.

Of the current twenty tallest competed buildings in the world, 19 use composite

or reinforced concrete structural systems; and the only structural steel system on

the top 20 list has a completion date prior to 1975. An even better indicator is

that of the 20 tallest buildings completed in 2018, all used composite or

reinforced concrete systems (data as per the Council of Tall Buildings and Urban

Habitat, www.ctbuh.org). Reinforced concrete construction has an inherent

advantage for tall building design, in that it provides a substantial amount of

stiffness, and mass and damping for the structural; three factors that are critical in

controlling building motions and accelerations. This session demonstrates the use

of reinforced concrete as it pushes to new heights across the globe.

Learning objectives:

1. Characterize the advantages of using reinforced concrete for the design of super-tall structures;

2. Identify the aspects of high-performance concrete;

3. Differentiate between the local concrete practices in Mexico, the Middle East, and Seoul; and

4. Describe structural systems employed for super-tall reinforced concrete structures.

Presentation 1—Concrete Pushes Mexico to New Heights Roberto Stark, President, Stark & Ortiz, S.C.

Urban areas are getting more crowded every day. The construction of tall buildings

is increasing due to expensive lands, and there is a need to keep all the utilities and

infrastructure condensed in a smaller area. At the same time, the tendency is to

avoid the use of automobiles inside the cities to help reduce pollution and hours of

nonproductive activity.

The United States was the first country to start this movement, mainly in New York

and Chicago. Recently, other countries such as Korea, Japan, and China are also

joining this trend. On the other hand, in countries such as United Arab Emirates

and Saudi Arabia, the main purpose is to construct these types of buildings to

create a landmark for the city.

The talk will be focused on the description of the tallest building in Mexico: Torre

Koi. Torre Koi is considered the tallest concrete building in Latin America.

Presentation 2—Recent Supertall Concrete Towers in the Middle East Robert Sinn, Principal, Thornton Tomasetti; & John Peronto, Senior Principal, Thornton Tomasetti

The Middle East is a location where the will

to build tall is readily apparent. Cast-in-

place reinforced concrete is the material of

choice there for supertall towers to an

almost exclusive degree. Two projects—the

Jeddah Tower in Saudi Arabia and the Dubai

Multi Commodities Centre (DMCC) Uptown

development in Dubai—are presented as

outstanding examples of contemporary

supertall and ultra-tall concrete structures

supporting a modern architectural aesthetic

of iconic exterior forms. The development

of the structural systems as well as details

of the high-strength concrete material and

construction technology implementation are highlighted for these two large master-planned developments.

Presentation 3—Design Using High-Performance Concrete and Construction Method for Lotte World Tower in Seoul Edward Roberts, Senior Associate, LERA Consulting Structural Engineers

The Lotte World Tower is the first supertall building in South Korea. The 123-story, 555 m (1820 ft) tower was designed by Kohn Pedersen Fox Associates and LERA Consulting Structural Engineers of New York. The composite structural system uses high-strength concrete core walls and mega-columns, as well as steel outrigger and belt trusses. Due to the tower’s tapering shape, each floor plan is unique, each column slopes in two directions, and the concrete core walls slope in the middle third of the tower. This presentation will discuss the structural design decisions made in response to the tower’s unique challenges.

Session 4: Changes in ACI 318-19, Part 2 of 2 Moderated by Jim Cagley, ACI Past President, Principal, Cagley & Associates, Inc.

This session includes a continuing review of the changes included in ACI 318-19 as well as a presentation on the issues arising from the 2016 Kaikoura Earthquake in the New Zealand Guidelines resulting from the earthquake. Learning objectives:

1. A brief review of the new Appendix A in ACI 318-19, A Design Verification Using

Nonlinear Response History Analysis;

2. A review of the changes in Chapter 18 – Earthquake-Resistant Structures;

3. Issues identified in the 2016 Kaikoura Earthquake in New Zealand; and

4. Presentation of the new guidelines for the seismic assessment of existing buildings

with precast floors.

Presentation 1—Design Verification Using Nonlinear Response History Analysis Luis Garcia, ACI Past President, Professor (retired), Universidad de los Andes

This new appendix applies to the design of structural concrete in structures assigned to Seismic Design Categories B through F that are designed using results of nonlinear dynamic analyses under multiple earthquake ground motions calibrated to represent maximum considered earthquake shaking that is acceptable for determining design requirements and verifying the anticipated adequacy of a design considering earthquake ground motions representing the seismic hazard at a site. Nonlinear dynamic analysis at an appropriate hazard level, for example, at the Risk-Targeted Maximum Considered Earthquake (MCER) of ASCE 7, can be used to supplement more traditional linear design methods.

Presentation 2—New Seismic Provisions in Building Code John Wallace, Professor, University of California at Los Angeles

A host of new code changes have been approved for adoption in Chapter 18 – Earthquake-Resistant Structures, of ACI 318-19 to address a variety of issues. The most significant changes focus on improving the performance of special structural walls subjected to strong shaking, including: 1) amplifying ASCE 7 wall shear demands; 2) adjusting locations where longitudinal reinforcement may be terminated over the wall height; 3) revising boundary element and web transverse reinforcement within the plastic hinge region to require overlapping hoops and web crossties; 4) requiring a minimum area of boundary longitudinal reinforcement; 5) placing restrictions on splices of boundary longitudinal reinforcement at the critical section; 6) checking that the expected wall deformation capacity exceeds the expected wall drift demand; and 7) introducing a definition of a new system, referred to as a ductile coupled wall and proposing values for R, Cd, and Ω0 for

adoption in ASCE 7. Other significant changes include allowing the use of high-strength reinforcement, with some limitations, to resist flexural, axial, and shear demands in special seismic systems and introducing new requirements for the seismic design of diaphragms constructed using both topped and untopped precast concrete members. Finally, requirements were relaxed for roof-level column-to-beam strength ratios and for detailing of gravity columns. The presentation will provide a summary of these changes and the associated technical background.

Presentation 3—Damage to Concrete Buildings with Precast Floors during the

2016 Kaikoura Earthquake Ken Elwood, Professor, University of Auckland

The 2016 Kaikoura earthquake in New Zealand resulted in shaking in excess of

design level demands for buildings with periods of 1 to 2 seconds at some

locations in Wellington. This period range correlated to concrete moment frame

buildings of 5 to 15 stories, many of which had been built in Wellington since the

early 1980s, and often with precast concrete floor units. Varying degrees of beam

hinging and residual beam elongation were observed. Cases of significant beam

elongation and associated support beam rotation resulted in damage to precast

floor unit supports—in one case leading to loss of support for double-tee units.

The deformation demands also resulted in damage to floor diaphragms, especially

those with hollow-core floor units. Cracking in floor diaphragms was commonly concentrated in the corners of the

buildings. Transverse cracking of hollow-core floor units was identified as a particular concern. Following the

earthquake, a guideline was developed for the seismic assessment of existing buildings with precast floors. This

presentation will discuss damage from the Kaikoura Earthquake and the implementation of seismic assessment

guidelines for buildings with precast floors in New Zealand.

International Workshop Reception & Young Practicing Engineer Poster Session Hosted by Jack Moehle, Professor, University of California at Berkeley, former Chair of ACI 318

Poster 1 - Ayia Napa Marina, Cyprus

Indira Oraziman, Project Engineer, Thornton Tomasetti

Thornton Tomasetti’s Ayia Napa Marina project in Cyprus contains two iconic towers on

the Mediterranean coast.

Over 110 meters tall, both towers consist of twisting T-shaped floor plates and sloping

helical columns around the perimeter. Each floor plate is rotated approximately 1.6

degrees in plan (40 degrees overall) relative to the floor below until the upper two

penthouse levels that are stacked vertically. The columns follow the slab rotation in both

directions creating helical shape. This sloping geometry of all the columns in the same

direction creates a horizontal component from the axial gravity force that is imposed into

the slab plate creating a twisting motion in the tower, which is then transferred into the

concrete circular shear walls.

In addition to the shear form torsion, the site is located in a moderately high seismic

zone of Mediterranean coast and per Eurocodes design shear forces from earthquake

have to be increased by 50% in the wall critical zone. The combined horizontal shear force from the building self-

weight and the lateral seismic loads was resolved by a structural system comprising of (1) conventionally

reinforced concrete shear walls with a thickness of 750m connected by coupling beams and (2) augmented by a

ductile perimeter reinforced concrete moment frame that reduced the torsional forces imposed on the core.

Although, there are some steel elements used in the project, introducing a reinforced concrete core walls as the

main structural system has helped to decrease the cost of the project significantly by avoiding a necessity to

import steel elements to the island.

Building movement was another challenge to address during the design. An extensive analysis was conducted

using nonlinear construction sequence approach in ETABS software, in order to take into consideration long-term

effects of concrete on the building’s rotation and its impact on façade and vertical transportation systems. The

study conducted that the rotational displacement of the core shall not be compensated during construction.

However, bearing in mind sensitivity of the analysis, it was proposed and agreed by all project parties (developer,

contractor, and design teams) on the absolute need for structural monitoring and continuous co-operation during

the erection.

Construction Documents were recently completed for both towers by TT and the construction of the East Tower is

now well underway.

The Ayia Napa Marina development project was awarded to TERNA S.A. who is serving as the project’s General

Contractor.

Poster 2 – Cracking Analysis of Elevated Railway RC Piers Due to Train-Induced

Vibrations at an Early Age Santiago Bertero, Structural Engineer, LABDIN

One of the main goals during construction of the new elevated railway connecting

the city of Buenos Aires with its suburbs to the west was to keep the former

ground-level railroad in service. However, this meant that the current line would go

through directly in-between the Elevated rail’s piers until the whole structure was

ready. Particularly worrisome was the possibility that vibrations produced by trains

on the ground-level railroad would crack recently built RC piers before they could

gain full strength. In response, trains were travelling at a lower speed. In order to evaluate the piers (frame structures with single pile foundations) at early

stage, several tests were carried out on those that had already gained full strength.

First, train-induced vibrations were measured on the rail, on the ground near the

foundation, and on top of one of the pier’s columns. Operational modal analysis

was also carried out to obtain natural frequencies for in-plane and out-of-plane

flexural modes. As personnel safety was of deep concern, wireless accelerometers were developed to be placed on

top of the 8m tall piers. Modal parameters obtained from both train-induced and ambient vibrations were used to calibrate an analytical

structural model at 28 days. Concrete properties were taken from previous sample tests, so the main unknown

was the embedded length of the columns to the ground. With said model calibrated – and with the available data

for concrete at 3 days – the modal parameters for the RC piers at an early age were estimated. Measurements of vibrations at the rail level and on top of the piers made it possible to fully represent the loading

due to trains passing by. That information was then inserted in the calibrated analytical model, obtaining in-plane

and out-of-plane moments for the frame structure. These moments were compared against cracking moments

found in ACI 318. Results show that moments were significantly lower than those required to produce cracking on

the RC piers at an early stage. As such, no further action was required, and trains could go back to passing through

at full speed while construction took place.

Poster 3 – Grand Hyatt SFO Hotel Kion Nemati, Structural Engineer, Arup

Kion Nemati’s poster will be a presentation of the Grand Hyatt SFO Hotel Project

– he is the project engineer. It will include photos of the actual building, both in

construction and substantial completion. Additionally, floor plans and a

perspective of the structure will be presented to provide the viewer a clear

understanding of the building and its structural systems. A brief project

description will be provided and will include a list of key structural elements.

Lastly, a list of (3) innovations on the project will be given, these will both cover

why the project was innovative and highlight the unusual degree of responsibility

placed upon the project engineer.

Poster 4 – Design of a Post Tensioned Flat-Slab Bridge

Umut AKIN, Structural Design Engineer, SU-YAPI Engineering & Consulting Inc.

In this project, the design of a post-tensioned highway bridge composed of two spans with 33.175m and 22.575m lengths is carried out. The bridge also has a variable width, widening from 28.98m to 31.98m. A solid, thin deck solution with a height of 1100mm is preferred in accordance with the architectural and functional details of the structure. The structural analysis is performed in Midas software, whereas the structural design is conducted in compliance with the latest Eurocode Standards and local (Dutch) annexes. Construction drawings are being prepared in BIM environment, taking into consideration all geometrical characteristics of the bridge geometry, post-tensioning tendons and the surrounding environment. Although the design is performed considering a structural service life of 100 years,

the future possible service conditions in addition to current planning is taken into

consideration in the design of the structure.

Poster 5 - Reduce, Reuse, Recycle – Concrete

Ashley Gaur, Design Engineer, Englekirk

Brentwood Gateway is a 10-story above-grade reinforced concrete office tower built in the 1970s and was tagged as a non-ductile concrete building by LA City. The existing lateral system consists of concrete moment frames in both orthogonal directions. Through the use of ASCE 41, the existing lateral system was analyzed to its maximum capacity and retrofitted to accommodate and adhere to new code requirements. Along with the tower structure, a neighboring parking structure was analyzed with ASCE

41 as well. Unlike the tower, the existing lateral system (concrete moment frames) of

the parking structure was not adequate to sustain the required lateral forces. This

resulted in the introduction of an entirely new lateral system, consisting of concrete

shear walls. The design was completed prior to the publication of the information

bulletin by LADBS, causing the project to be used as a precedent for official analysis

requirements that would apply to similar projects in the future.

Poster 6 - IQON Tower: Modeling and PBSD of Tall Building with Friction Dampers

in Quito

Jorge Bustos Silva, Structural Engineer, Rene Lagos Engineers

As a part of the Seismic Technologies team of René Lagos Engineers, EOC for the project, young Engineer Jorge Bustos was in charge of the modeling and design of IQON Tower, a mixed-use 32-stories RC Shear wall building, located in the city of Quito, Ecuador. By using Performance-based Seismic Design methods, Jorge was in charge of detailing, modeling and performing nonlinear dynamic analysis of the building using the software Perform 3D. Once finished, the building will be the tallest of the city and the first in the country to incorporate friction dampers. Building description: The lateral force resisting system consists of two RC shear wall cores at both ends of the floor plant, with RC columns resisting gravity loads, all connected by a posttensioned RC slab and a special set of dampers replacing coupling beams at each core. These dampers dissipate energy by friction caused by shear deformation. Design process: First, a linear model of the building in ETABS was used to size

structural elements and detail preliminary reinforcement, using modal spectral analysis for Service-Level specific demand, according to the document “An alternative procedure for seismic analysis and design of tall buildings located in the Los Angeles region” by Los Angeles Tall Building Structural Design Council (2018). Then a nonlinear model of the structure was made in Perform 3D, considering fiber modeling for walls, and plastic hinges for frame elements, analyzed under Maximum-Considered-Earthquake demand using time-history escalated earthquake data. As the addition of friction dampers was a budget-depending variable, Jorge was commissioned to come up with an optimal solution, by making many models, both with and without dampers, and different versions managing the amount and location of the dampers, while also taking into account architectural requirements. Results and lessons: In the end, an optimized version of the building was reached, that allowed savings in concrete and reinforcement volumes by using PBSD techniques to detect the vulnerable areas of the building (maximum yielding at mid-height), and also assured collapse prevention under extreme seismic loads. But also, by having an optimal distribution of the dampers, seismic performance was improved, for example reducing inter-story drifts by more than 30% (shown by comparative graphs of local and global deformation vs. building height). Currently the project is under construction, at the moment coming close to podium level.

Poster 7 - Inspection, Strengthening and Load Testing of a 63-Year-Old Reinforced

Concrete Bridge Matheus Moyses Pain, Senior Civil Engineer, EGT Engenharia

This poster describes the detailed inspections, structural checks, strengthening of

damaged girders, static and dynamic field measurements performed at the

Freguesia do Ó Bridge, a reinforced concrete bridge inaugurated in 1956, with total

length of 240m (787ft) and 25m (82ft) width, subject to intense and heavy

traffic. Distributed on the banks of the Tietê River, it has a 3-beam-grid structure in

8 different spans varying from 7m (23ft) to 17m (56ft), a 71.5m (235ft) tri-hinged

arch over the river and a 25m (82ft) precast alveolar slab extension.

The works developed are part of the emergency inspections program of São Paulo

City Government, in Brazil, which aims to verify the safety conditions of old bridges

throughout the city.

Poster 8 – Performance-based Design Yields System Efficiency

Jaskanwal Chhabra, Structural Engineer, Skidmore, Owings & Merrill LLP

95 State at City Creek project consists of a new Class A office tower located in the financial district of Salt Lake City, Utah. The proposed building structure consists of 25 stories above grade with a tall roof parapet level and one below grade basement level. Levels 1 to 5 form a podium with larger floor areas encompassing meeting house program facilities. The office building tower extending from Levels 6 to 25 is typically rectangular in plan formed with slight curved edges and rounded corners. Top of parapet is expected to be at 392'-3" above existing grade. The superstructure construction incorporates a reinforced concrete core wall system that exceeds the height limit of 240 feet per ASCE 7-16 and as such, an alternate design method using performance-based seismic design procedure is adopted following the guidelines of the PEER TBI v.2.03 (2017) “Guidelines for Performance-Based Seismic Design of Tall Buildings" under the technical review of an independent seismic design

review panel. The author was the lead analytical engineer in developing the non-linear analysis model of the tower, designing its lateral load resisting system and evaluating its seismic performance. The poster will summarize the key lessons learned during the performance-based design of the tower. Key contributions of the project involved: 1) design of an efficient and well-proportioned lateral load resisting coupled-core wall system that could dissipate seismic energy by controlled yielding of the coupling beams and hinging at the base of the building core, 2) explicit modeling of the soil-structure interaction to capture the maximum backstay effects and determine the upper-bound demands on transfer diaphragm, and 3) design of the steel mechanical penthouse structure at the roof of the tower as an integral sub-component of the tower. In the initial design phases, a preliminary design of the tower was generated based on linear elastic methods. However, on the basis of the response of the tower in the non-linear analysis the design team decided to intentionally: 1) reduce the link beam reinforcement in order to ensure distributed energy dissipation up the height of the building, 2) introduce additional coupling beams by adding openings in the core wall even when the opening was not programmatically required, and 3) re-proportioning the core wall boundary-zone rebar in order to force the hinging at the base of the building. All these steps resulted in a relatively flexible structure that attracted less seismic shear and dissipated more seismic energy while keeping the drifts in control. The design team decided the explicitly model the vertical flexibility of the foundation system and model the basement system with relatively higher in-plane shear stiffness. This was found to be crucial in determining the upper bound demands on the transfer diaphragm and it was observed that not modeling foundation flexibility and the stiff backstay could be

underestimating the diaphragm demands by more than 100%. Furthermore, above the roof level (El. +356'- 6") lateral and gravity systems consist of steel framed core, roof mechanical penthouse, screen walls and perimeter glazed wall enclosure. It was observed that the steel bracing in the mechanical penthouse at the roof of the tower can attract significant forces while maintaining deformation compatibility with the concrete core of the tower below the roof level. Hence in-lieu of designing the steel penthouse at the roof as an independent non-structural component, the design team chose to model it in the non-linear model of the tower and design it as a structural component. The construction of the tower is anticipated to complete in early 2022.