An Innovative Prefabricated Steel Structure System De Ming (Derry) Yu, Project Director, New World China Land Co. Ltd.
Table of Contents 1. Main Problems in Current Steel Structure Connections & Our Proposal 2. Origins of Tenon-mortise Joint & the Seismic Performance of Timber Structure 3. Proposal for a New Prefabricated Steel Structural System 4. Application Example for Temporary Structure-Hoarding 5. Conclusions 6. Issues to be further explored and studied
1. Main Problems in Current Steel Structure Connections & Our Proposal 1.1 Problems for High Strength Bolt Connection For high strength bolt connection, each joint may need to drill dozens or even hundreds of bolt holes on the members to be connected and the connecting plates in advance, it s very time-consuming and costly. Errors usually will occur for steel members during fabrication, and sometimes it will result in the difficult connection on site due to the accumulated errors from different components and fabrication processes. Manual fixing for bolts are required, For fixing each bolt, three working procedures may be needed: that is, temporary fixing, initial and final tightening, which will greatly increases on-site workingload and cost.
1.2 Problems for Welding Connection Onsite For welding connection onsite, usually pre-heating will be required prior to welding in case of thick plate or low environmental temperature, which will increases the onsite workingload and cost; Onsite welding also will be easily affected by welder s experience and proficiency, welding procedure and environment such as weather condition and welding position etc., it will lead to the difficulty for ensuring good quality for on-site welding. Extensive welding onsite will be very time consuming and risky.
1.3 Our Proposal Innovative Prefabricated Steel Structure System improved from tenon-mortise joint of timber structure; Possess sound structural safety & excellent seismic performance; Realize simplified & standardized modular fabrication for steel members & connections; Realize rapid No-bolt No-welding installation onsite; Significantly reduce construction time (20~30%) and cost;
2. Origins of Tenon-mortise Joint & the Seismic Performance of Timber Structure 2.1 Origins of Tenon-mortise Joint The Hemudu Site located in Yuyao City of eastern China belongs to Neolithic Age of more than 7,000 years ago, since the archaeological excavation from 1973, a lot of timber tenons and mortises had been found in the site, it means the Tenon-mortise joint had already been skillfully mastered and widely adopted to build dwellings at that time. Reference: GAO D.F., ZHAO H.T. & XUE J.Y. (2008). Study on Chinese Ancient Timber Structure and its Seismic Performance. (in Chinese) Beijing: China Science Press. Tenons and Mortises Found in the Hemudu Site
2.2 Seismic Performance of Existing Ancient Timber Structures in China The Yingxian Timber Tower constructed in 1056 is located in Shanxi Province of China. The 67.31m high tower is octagonal in plane with bottom diameter 30.27m, it is still intact after suffered many strong earthquakes including more than 10 earthquakes with Seismic Intensity over 5-degree. Yingxian Timber Tower - Shanxi The Hall of Supreme Harmony - Beijing The Hall of Supreme Harmony is located within the Forbidden City of Beijing, China. It was firstly completed in 1420 and then reconstructed after suffered several fires, the current one was constructed in 1695. It is 26.92m high, 64m long and 37m wide with total area 2377m 2. It had suffered 7 times of strong earthquakes with Seismic Intensity over 6-degree since 1695. No damage occurred even if under a 8-degree earthquake with epicenter only 45km away in 1679.
2.2 Seismic Performance of Existing Ancient Timber Structures in China Shoulder Tenon-Mortise Dovetail Tenon-Mortise These 2 existing acient timber structures had clearly proved the structural safety and excellent seismic performance of timber structures. One of the most important factors is the Tenon-mortise connection (see figures in the left) had been adopted as the joints, and furthermore due to the light weight, good ductility and strong energy dissipation capacity of timber material, plus the deformation and frictional sliding between tenons and mortises could balance, absorb and ultimately dissipate the seismic energy such that to secure the structural safety and integrity. Of course, based on the fundamental concepts of current seismic design theory, timber structures with Tenon-mortise joint need to be further improved, such as how to secure strong joint weak components when the tenon s nodes section is weakened compared with the corresponding component, and how to minimize floor vibration, control deformation etc.
3. Proposal for A New Prefabricated Steel Structural System Proposed Steel Structure System Mainly Includes: -Column ; Main-Secondary Beam Connection; Connection Between Steel Beam and Concrete Wall & Column; Energy Dissipation Type Rebar Brace; Non-structural Tie-column & Tie-beam Connection;
3.1 Beam-Column Horizontal Stiffener Fixing Plate Horizontal Stiffener Upper Steel Column Beam-Column Lower Steel Column Disassembled Components for a Beam-Column Joint Fixing Plate Vertical Stiffener Shear Key End Elevation Horizontal Stiffener Horizontal Stiffener Inner stiffeners inside Box-section Sleeve
3.1 Beam-Column Beam-Column Longitudinal Section A A B B Rebar Brace Fixing Plate with slot hole C-Section Sleeve Insert Fixing Plate with V-Shape Ends into the Notches of C-section Sleeve to lock the in position Section A-A Fixing Plate Fixing Key Elevation of the and Section B-B
3.1 Beam-Column (Video ) Beam-Column Step 1 Step 2 Step 3 Step 4 Lower Steel Column Upper Steel Column Fixing Plate Optional Measure Thickness<3mm Adopting steel cleat to fine-tune column position if necessary; Applying structural steel adhesive on the contact surfaces to enhance the seismic resistance & ductility of the connection; Installation Sequence of a Beam-Column Joint
3.2 Main-Secondary Beam Connection-Type A: Dovetail Type A Dovetail Tenon Connecting Plate Secondary Beam Main-Secondary Beam Disassembled Components for a Main- Secondary Beam Joint Using Dovetail Mortise Connecting Plate (Type A ) A 3D Perspective View Dovetail Groove with Leaning Angle on the connection plate to prevent slipping of the connecting Secondary Beam Secondary Beam Section A-A
3.2 Main-Secondary Beam Connection-Type A: Dovetail Type Secondary Beam A Plan Secondary Beam Main-Secondary Beam A Connection between & Secondary Beams Using Dovetail Mortise Connecting Plate (Type A) Main-Secondary Beam Secondary Beam Secondary Beam Vertical Stiffeners Main-Secondary Beam Vertical Stiffeners Section A-A Dovetail Tenon Connecting Plate (For same main & secondary beam depth ) Dovetail Groove Connecting Plate Dovetail Tenon Connecting Plate (For different main & secondary beam depth ) Dovetail Groove Connecting Plate
3.2 Main-Secondary Beam Connection-Type A: Dovetail Type Cantilever Edge Beam Positioning Steel End Plate Edge Beam Cantilever Beam Edge Beam A A Positioning Steel End Plate Main-Secondary Beam Edge Beam Cantilever Beam Cantilever Beam 3D Perspective View Main-Secondary Beam Plan Connection between Cantilever Beam & Secondary Beams Using Dovetail Mortise Connecting Plate (Type A) Section A-A Positioning Steel End Plate
3.2 Main-Secondary Beam Connection-Type A: Dovetail Type(Video ) Secondary Beam Secondary Beam Main-Secondary Beam Shear Studs Main-Secondary Beam Step 1 Step 2 Installation Sequence of Secondary Beam to Using Dovetail Mortise Connecting Plate (Type A)
3.2 Main-Secondary Beam Connection-Type B: Sleeve Type Secondary Beam Notches at Both Top & Bottom Flanges of the C-section Sleeve Secondary Beam Main-Secondary Beam Section A-A A A 3D Perspective View Secondary Beam Fixing Plate Main-Secondary Beam Secondary Beam Fixing Plate C-section Sleeve for Main Beam to connect with Secondary Beam Insert Fixing Plate with V-Shape Ends into the Notches of C-section Sleeve to Lock the Secondary Beam in Position Disassembled Components for a Main-Secondary Beam Joint Using C-section Sleeve (Type B)
3.2 Main-Secondary Beam Connection-Type B: Sleeve Type Main-Secondary Beam Secondary Beam A Plan Connection between & Secondary Beams Using C-section Sleeve (Type B) A Secondary Beam Secondary Beam Main-Secondary Beam Main-Secondary Beam Section A-A Vertical Stiffeners Vertical Stiffeners Secondary Beam (For same main & secondary beam depth ) Secondary Beam (For different main & secondary beam depth )
3.2 Main-Secondary Beam Connection-Type B: Sleeve Type Cantilever Cantilever Beam Plan Edge Beam Main-Secondary Beam A Positioning Steel End Plate A Edge Beam Edge Beam Positioning Steel End Plate Cantilever Beam Main-Secondary Beam 3D Perspective View Cantilever Beam Section A-A Positioning Steel End Plate Secondary Beam Fixing Plate Edge Beam Connection between Cantilever and Secondary Beams Using C-section Sleeve (Type B)
3.2 Main-Secondary Beam Connection-Type B: Sleeve Type(Video ) Secondary Beam Secondary Beam Fixing Plate Secondary Beam Main-Secondary Beam Installation Sequence of Secondary Beam to Using C-section Sleeve (Type B) Shear Studs Main-Secondary Beam Step 1 Step 2 Step 3
3.3 Connection between Steel Beam & RC Core Wall/Column For Composite Structure Type A Dovetail Type Connection 3D View Type B Sleeve Type Connection 3D View RC Wall/Column Anchor Bars Type A Connection Elevation Steel Embed Plate RC Wall/Column Steel Embed Plate Steel End Plate Steel Beam Steel Connection Sleeve Steel Beam Anchor Bars Fixing Key Type B Connection Elevation
3.4 Energy Dissipation Type Rebar Brace & Connection to the Beam-column Joint Energy Dissipation Coupler High Strength Rebar Brace Energy Dissipation Type Rebar Brace High Strength Rebar Brace Put the hooks of the 2 rebar rods into the slot hole of the rebar brace fixing plates which are pre-welded at the corners of beam-column connection sleeve in factory. The energy dissipation coupler could adopt either rod type viscous damper or low-yield high-ductility soft steel. Common high strength rebar (Grade HRB500 in Chinese) has ultimate tensile strength over 630MPA. For a single 50mm diameter rebar, the ultimate tensile resistance can be over 1230kN. The hot rolled steel bar Grade PSB1080 produced in China has ultimate tensile strength over 1230MPa. For a single 50mm diameter rebar, the ultimate tensile resistance can be over 12400kN. If necessary, numbers of high strength rebar can be bundled to form the brace.
3.4 Energy Dissipation Type Rebar Brace & Connection to the Beam-column Joint Rebar Brace Fixing Plate High Strength Rebar Brace Rebar Brace Fixing Plate Rebar Brace Fixing Plate High Strength Rebar Brace Rebar Brace Fixing Plate Rebar Brace Fixing Plate High Strength Rebar Brace Typical Rebar Brace Application Cases Rebar Brace Fixing Plate
3.5 Column Base Connection Pinned End Fixed End Traditional Column Base connection detail to be Adopted Column Base
3.6 Non-structural Tie Column Connection-H Section (Video ) Tie Column Fixing Keys Steel Beam H-section Tie Column Installation Sequence for H-section Tie Column (Type A) Step 1 Step 2
3.6 Non-structural Tie Column Connection-Channel Section (Video ) Tie Column Fixing Keys Steel Beam Channel-section Tie Column Insert Steel Cleat into the Gap between Tie Column Web & Fixing Key to Enhance the Fixing Step 1 Step 2 Installation Sequence for Channel-section Tie Column (Type B)
3.7 Non-structural Tie Beam Connection-H Section (Video ) H-section Tie Beam Tie Beam Fixing Keys Steel Column Installation Sequence for H-section Tie Beam (Type A) Step 1 Step 2
3.7 Non-structural Tie Beam Connection-T Section (Video ) T-section Tie Beam Tie Beam Fixing Keys Steel Column Installation Sequence for T-section Tie Beam (Type B)
3.8 Extended Application to RC Structures Cast-in Steel Strip for Fixing Shear Stud Cast-in Rebar Steel Embed Plate at the Top of Beam Tip Precast RC Beam Cast-in Rebar Fixing Key Welded on the Bottom of Steel Embed Cast-in Rebar Precast RC Beam Cast-in Steel Strip for Fixing Shear Stud Cast-in Rebar Beam Tip Top Plan Precast RC Beam 3D Perspective View Steel Embed Plate at the Bottom of Beam Tip Detail of a Precast RC Beam Tip Beam Tip Bottom Plan
3.8 Extended Application to RC Structures Precast RC Column Fixing Groove at the Surface of Steel Embed Plate to Enhance the interlocking Steel Embed Plate at the Column Tip Steel Embed Plate Cast-in Rebar Groove at the Surface of Steel Embed Plate Steel Embed Plate at Column Tip Cast-in Rebar Fixing Groove at the Surface of Steel Embed Plate 3D Perspective View Precast RC Column Tip Section Detail of a Precast RC Column Tip Precast RC Column Tip Elevation
3.9 Extended Application to Timer Structures Timber Beam Timber Beam 3D Perspective View Steel or Timber Shear Key Fixed by Flat Head Bolt / Steel Nail Flat Steel Bolt / Steel Nail Flat Head Bolt / Steel Nail Steel or Timber Shear Key Fixed by Flat Head Bolt / Steel Nail Steel or Timber Shear Key Fixed by Flat Head Bolt / Steel Nail Beam End Elevation Beam End Bottom Plan Timber Beam Detail of a Timber Beam Tip
4. Application Example for Temporary Structure-Hoarding (Video ) An attempt for practical application Traditional Hoarding CTBUH Comparison for Constructing a 400m Long Hoarding (Site Area 10,000m 2 ) Required Steel Tonnage Proposed Hoarding Equivalent Steel Cost Each Time Cost for Repeated Use 3 Times Required Time for Installation Saving Time Traditional Method 220 ton 0.55 ton/m USD418,000 USD1,900/ton Proposed Method 256 ton 0.64 ton/m (+16%) USD486,400 USD1,900/ton & Steel Cost 1 If the Hoarding could be repeatedly used for 3 Times, the cost for Each Time will be 39% of traditional one; 2 The installation time for a 3-span 7.2m length hoarding is 2.5 hours, saving 40~50% time compared with traditional one; N/A USD162,133 (=USD486,400/3) 150 Days 90Days 0-60 Days (-40%) USD255,867 (-61%)
5. Conclusions 1. To solve the problems in current steel structures connection, by adopting connection joints similar to but improved from Tenon-mortise joint of ancient timber structure with enhanced seismic performance, an innovative prefabricated steel structure system is proposed; 2. The most attractive feature of this system is: all of the structural members and connection joints could be easily fabricated in factory with secured good quality; simple & fast Nobolt No-welding Installation onsite could be realized efficiently; 3. Less fabrication process, shorter construction period could help to push energy conservation & emissions reduction, and expedite green construction and more sustainable building industry; 4. Through standard design, modularized fabrication and simplified installation, increasing labor shortage & soaring construction cost could be relieved, and eventually facilitate the industrialization & popularization for prefabricated structures;
6. Issues to be Further Explored and Studied 1. To conduct more theoretical studies & simulations for the connection joint and the overall structure system for further improving the details; 2. To conduct static & dynamic tests for the connection joints & different structural models, to verify the structural behaviors including deformation characteristics, failure process & seismic performance etc.; 3. To push both fabricators and steel-casting factories to adopt high-speed, high precision and intelligent Numerical Control machining technology and BIM technology, so as to upgrade fabrication efficiency & accuracy; 4. To develop low-cost, high temperature resistant structural steel adhesive, so as to avoid the thermal and oxidative decomposition of conventional steel adhesive under fire, and further enhance the overall energy dissipation capacity by applying it to the joints; 5. To develop efficient & stable 3D printing technology for steel, so as to further improve the prefabrication quality for connection sleeves and complex joints;
Granted Patents: Applied Patents: 1 Prefabricated Structural System PRC Patent No. 201721154686.5 Granted on 2018/03/30 2 Prefabricated Steel Tie Column and Tie Beam Members for Steel Structure System PRC Patent No. 201720373021.7 Granted on 2018/02/27 3 Prefabricated Brace for Steel Structure System PRC Patent No. 201720372983.0 Granted on 2018/02/27 4 Prefabricated Structural System HK Patent No. HK1245574 Granted on 2018/08/24 Applicant: New World China Land Limited 9/F, New World Tower 1 18 Queen's Road Central Hong Kong, China 1 Prefabricated Structural System and Assembling Method Thereof PRC Application No. 201710104308.4 Submitted on 2017/02/24 US Application No.15/903.384 Submitted on 2018/02/23 EU Application No.18158225.5 Submitted on 2018/02/22 Japan Application No.2018-030876 Submitted on 2018/02/23 2 Prefabricated Steel Beam Connection with RC Wall or Column PRC Application No. 201820405954.4 Submitted on 2018/03/26 Inventors: YU, De Ming Derry LU, Wenjie Michael KONG, Kam Ching Ivan derryyu@nwcl.com.hk michaellu@nwcl.com.hk ivankong@nwcl.com.hk
THANK YOU! 谢谢! Q & A