Faculty of Engineering

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1 e Faculty of Engineering SEISMIC PERFORMANCE OF LOW-RISE PRECAST CONCRETE STRUCTURE WITH DIFFERENT TYPES OF BEAM-COLUMN CONNECTIONS USING NONLINEAR STATIC PUSHOVER ANALYSIS LIM HUNG LING Master of Engineering (Civil Engineering) 2013

2 UNIVERSITI MALAYSIA SARAWAK Grade: Please tick ( ) Final Year Project Report Masters PhD DECLARATION OF ORIGINAL WORK This declaration is made on the..day of Student s Declaration: I Lim Hung Ling, , Faculty of Engineering hereby declares that the work entitled Seismic Performance of Low-Rise Precast Concrete Structure with Different Types of Beam- Column Connections Using Nonlinear Static Pushover Analysis is my original work. I have not copied from any other students work or from any other sources except where due reference or acknowledgement is made explicitly in the text, nor has any part been written for me by another person. Lim Hung Ling, Date submitted Name of the student (Matric No.) Supervisor s Declaration: I Mdm. Azida Rashidi. hereby certifies that the work entitled Seismic Performance of Low- Rise Precast Concrete Structure with Different Types of Beam-Column Connections Using Nonlinear Static Pushover Analysis was prepared by the above named student, and was submitted to the FACULTY as a * partial/full fulfilment for the conferment of Master of Engineering, and the aforementioned work, to the best of my knowledge, is the said student s work. Received for examination by: Mdm. Azida Rashidi Date:

3 I declare that Project/Thesis is classified as (Please tick ( )): CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)* RESTRICTED (Contains restricted information as specified by the organisation where research was done)* OPEN ACCESS Validation of Project/Thesis I therefore duly affirmed with free consent and willingness declare that this said Project/Thesis shall be placed officially in the Centre for Academic Information Services with the abiding interest and rights as follows: This Project/Thesis is the sole legal property of Universiti Malaysia Sarawak (UNIMAS). The Centre for Academic Information Services has the lawful right to make copies for the purpose of academic and research only and not for other purpose. The Centre for Academic Information Services has the lawful right to digitalise the content for the Local Content Database. The Centre for Academic Information Services has the lawful right to make copies of the Project/Thesis for academic exchange between Higher Learning Institute. No dispute or any claim shall arise from the student itself neither third party on this Project/Thesis once it becomes the sole property of UNIMAS. This Project/Thesis or any material, data and information related to it shall not be distributed, published or disclosed to any party by the student except with UNIMAS permission. Student signature (Date) Supervisor signature: (Date) Current Address: Notes: * If the Project/Thesis is CONFIDENTIAL or RESTRICTED, please attach together as annexure a letter from the organisation with the period and reasons of confidentiality and restriction. [The instrument is duly prepared by The Centre for Academic Information Services]

4 The following Thesis: Title : Performance of Low-Rise Precast Concrete Structure with Different Types of Beam-Column Connections Using Nonlinear Static Pushover Analysis Name : Lim Hung Ling Matric No. : Has been read and approved by: Mdm. Azida Rashidi (Supervisor) Date

5 SEISMIC PERFORMANCE OF LOW-RISE PRECAST CONCRETE STRUCTURE WITH DIFFERENT TYPES OF BEAM-COLUMN CONNECTIONS USING NONLINEAR STATIC PUSHOVER ANALYSIS LIM HUNG LING This project is submitted in partial fulfilment of the requirements for the Master of Engineering (Civil Engineering) Faculty of Engineering UNIVERSITI MALAYSIA SARAWAK 2013

6 Dedicated to Amy and my beloved family...

7 ACKNOWLEDGEMENT I would like to express a deep appreciation to my thesis supervisor, Mdm. Azida Rashidi who always provides good advices, supervision, guidance, and motivation throughout the study. I have great time on learning structural subject from her over the year. I also would like to extend my sincere appreciation to my dearest friends who helped me in solving some structural problems. We also keep exchanging our thoughts and findings all this while. With these, I am able to do a lot of progress in studying the structural theories. I

8 ABSTRACT Due to demand of speedy building construction and well controlled quality, precast concrete structure, being an Industrialized Building System, can replace the traditional construction method. However, the research on precast concrete structure in seismic zone is still requiring improvement. Hence, in this study, the types of beam-column connections are the main focus as the critical design parameter. Three three-storey two-dimensional precast concrete skeletal frames with three different types of beam-column connection, namely rigid, semi-rigid and pinned are modeled using structural analysis software, SAP2000V15. An earthquake excitation is simulated by applying a 10kN lateral force at a roof tip using the nonlinear static Pushover Analysis (based on FEMA356). The roof displacements of these frames versus increasing base shear are monitored and the resulting pushover curves are compared. A Seismic Demand Curve on probable earthquake in Malaysia is also constructed according to the code provision ACT-40. It is found that rigid frame can withstand the highest base shear and lowest storey drifts-joint displacement. However, a few of its beams and columns are badly damaged. The semi-rigid frame produces similar result to rigid frame with slight reduction in maximum base shear. The pinned frame can only withstand very low base shear with large storey drift-joint displacement. It collapses due to Soft Storey Mechanism where its columns at the base floor severely damaged while beams and columns above the base floor remain unaffected. When comparing capacitydemand curves of these three frames, the structural capacities of rigid frame and semi-rigid frame are able to meet seismic demand without severe damage. However, the structural capacity of pinned frame meets the seismic demand with severe damages in structural members. As a conclusion, the rigid and semi-rigid connections are suitable to be used in precast concrete skeletal structures in Malaysia. II

9 ABSTRAK Oleh kerana permintaan atas pembinaan bangunan yang cepat dan kualiti yang dikawal dengan baik, struktur konkrit pratuang, iaitu sejenis Sistem Bangunan Perindustrian, boleh menggantikan kaedah pembinaan tradisional. Walau bagaimanapun, penyelidikan pada struktur konkrit pratuang dalam zon seismik masih memerlukan pembaikan. Oleh itu, dalam kajian ini, jenis sambungan rasuk- tiang adalah fokus utama sebagai parameter reka bentuk yang kritikal. Tiga dua dimensi konkrit pratuang bingkai rangka yang bertingkat tiga dengan tiga jenis sambungan rasuk- tiang berlainan, iaitu tegar, separa tegar dan disematkan telah dimodelkan dengan menggunakan perisian analisis struktur, SAP2000V15. Satu ujaan gempa bumi adalah disimulasi dengan menggunakan daya sisi 10kN di hujung bumbung menggunakan Analisis pushover statik yang tak linear (berdasarkan FEMA356 ). Anjakan bumbung ini bingkai berbanding peningkatan ricih asas dipantau dan graf pushover terhasil dibandingkan. Satu graf permintaan seismik dari gempa bumi kemungkinan di Malaysia juga dibina mengikut peruntukan kod ACT-40. Ia didapati bahawa kerangka tegar boleh menahan asas ricih tinggi dan simpangan tingkat atau anjakan sendi terendah. Walau bagaimanapun, beberapa rasuk dan tiang didapati telah rosak teruk. Rangka separa tegar memberi hasil analysis yang agak sama dengan kerangka tegar dengan sedikit penurunan dalam ricih asas maksimum. Rangka disematkan hanya boleh menahan ricih asas yang sangat rendah dengan simpangan tingkat atau anjakan sendi besar tingkat. Ia runtuh disebab oleh kejadian 'Mekanisme Tingkat Lembut' di mana tiang di tingkat terbawah telah rosak dengan teruk manakala rasuk dan tiang di tingkat atas berkekal tidak terjejas. Apabila membandingkan kapasiti keluk permintaan bagi ketiga-tiga bingkai, kapasiti struktur kerangka tegar dan bingkai separa tegar dapat memenuhi permintaan seismik tanpa kerosakan teruk. Walau bagaimanapun, keupayaan struktur rangka disematkan masih memenuhi permintaan seismik dengan kerosakan teruk pada anggota struktur. Kesimpulannya, sambungan tegar dan separa tegar adalah sesuai untuk digunakan dalam konkrit pratuang struktur rangka di Malaysia. III

10 TABLE CONTENT Content Page Acknowledgement Abstract Abstrak List of Figures List of Tables I II III VIII XII List Page CHAPTER 1: INTRODUCTION 1.1 Introduction Problem Statement Significant of Study Objectives Scope of Study Brief Outline of the Structure of the Following Chapters Chapter Summary 8 CHAPTER 2: LITERATURE REVIEW 2.1 Introduction Precast Concrete Skeletal Frame 9 IV

11 2.3 Precast Concrete Beam-Column Connections Rigid Connection Semi-Rigid Connection Pinned Connection Comparison between Rigid, Semi-Rigid and Pinned Connections Methods of Seismic Analysis Pushover Analysis Response Spectrum Analysis Response History Analysis Precious Researches Formulating Semi-Rigid Behavior of Beam-Column Connections in a Precast Frame Comparing Behavior of Rigid Precast Concrete Beam-Column Connection and Monolithic Beam-Column Subjected to Reversed Cyclic Loads Effects of Plastic Hinge Properties in Nonlinear Analysis of Reinforced Concrete Buildings Chapter Summary 31 CHAPTER 3: METHODOLOGY 3.1 Introduction Verification Verification of Fixity Ratio Formula Verification of Non-linear Pushover Analysis Steps Using SAP Parameters of Three-Storey Two-Dimensional Precast Concrete Skeletal Frame 42 Model Under Study 3.4 Nonlinear Static Pushover Analysis Pushover Analysis Flow Chart Steps of Modeling and Analyzing Three-Storey Two-Dimensional Precast Concrete Skeletal Frame Using SAP Chapter Summary 62 V

12 CHAPTER 4: RESULTS AND DISCUSSION 4.1 Introduction Results from Three Storey Two Dimensional Structural Frames with Different Beam-Column Connection Pushover curves Pushover Curve For three Storey two-dimensional Precast Structural Frame with Rigid Beam-Column Connections Pushover Curve for Three Storey Two-Dimensional Precast Structural Frame with Semi-Rigid Beam-Column Connections Pushover Curve for Three Storey Two-Dimensional Precast Structural Frame with Pinned Beam-Column Connections Comparison of Pushover Curves (Figure 4.1, 4.2 and 4.3) Discussion on Comparison of Pushover Curves (Figure 4.4) Capacity-Demand Curves Capacity-Demand Curve for Three Storey Two-Dimensional Precast Structural Frame with Rigid Beam-Column Connections Capacity-Demand Curve for Three Storey Two Dimensional Precast Structural Frame with Semi-Rigid Beam-Column Connections Capacity-Demand Curve for Three Storey Two Dimensional Precast Structural Frame with Pinned Beam-Column Connections Comparison of Capacity-Demand Curves (Figure 4.10, 4.11 and 4.12) Discussion on Comparison of Capacity-Demand Curves (Figure 4.13 and Table 4.2) Plastic Hinge Formation Plastic Hinge Formation for Three Storey Two-Dimensional Precast Structural Frame with Rigid Beam-Column Connections Plastic Hinge Formation for Three Storey Two-Dimensional Precast Structural Frame with Semi-Rigid Beam-Column Connections 81 VI

13 Plastic Hinge Formation for Three Storey Two-Dimensional Precast Structural Frame with Pinned Beam-Column Connections Plastic Hinge Formation Analysis (Figure 4.14, 4.15, 4.16, 4.17, 4.18, 4.19 and 4.20) Discussion on Plastic Hinge Formation (Figure 4.14, 4.15, 4.16, 4.17, 4.18, 4.19, 4.20 and Table 4.4) Chapter Summary 87 CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS 5.1 Introduction Conclusion Recommendations 91 REFERENCE 92 VII

14 LIST OF FIGURES List Page Figure 1.1 A Collapsed Building in Japan s 1995 Kobe Earthquake 5 Figure 2.1 Precast Skeletal Frame 10 Figure 2.2 Example of Precast Braced Skeletal Frame 11 Figure 2.3 Types of Connections in a Precast Structure 12 Figure 2.4 Graphs for Classification of Moment-Resisting Connections as Fully Rigid, Semi-Rigid or Pinned/Flexible 16 Figure 2.5 Methods of Structural Analysis Used in Earthquake Engineering 18 Figure 2.6 Computation of Static Forces in Pushover Analysis 20 Figure 2.7 Steps in Response Spectrum Analysis 22 Figure 2.8 Example of Digitized Ground Motion Acceleration Record for El Centro 24 Figure 2.9 Example of Displacement of Roof vrsus Time 25 Figure 2.10 Hinge Locations at the Columns and Beams 30 Figure 3.1 Five-storey Precast Concrete Frame 34 Figure 3.2 Graph of Bending Moment at Column C1 versus Fixity Ratio by using SAP Figure 3.3 Result of Bending Moment at Column C1 36 Figure 3.4 Five Bay-Ten Storey Regular Reinforced Concrete Frame 37 Figure 3.5 Original Result from Chandrasekaran et al. (2010) 38 Figure 3.6 Remodeled Result Using SAP2000 v15 39 Figure 3.7 Comparison of Pushover Curves from Chandrasekaran et al. (2010) and from 39 Remodeled Frame Figure 3.8 SAP2000 v10 Used by Chandrasekaran et al. (2010) 40 Figure 3.9 SAP2000 v15 Used in This Study 41 VIII

15 Figure 3.10 Pushover Analysis Flow Chart 44 Figure 3.11 Three-Storey Three-Bay Two-Dimensional Precast Concrete Frame 45 Figure 3.12 Column s Property 46 Figure 3.13 Beam s Property 47 Figure 3.14 Load Pattern 47 Figure 3.15 Initial Pushover Load Case 48 Figure 3.16 Pushover Load Case 49 Figure 3.17 Distributed Loads 50 Figure 3.18 Three-Storey Two-Dimensional Frame with Assigned Distributed Loads 50 Figure 3.19 Three Storey Two-Dimensional Frame with Assigned Lateral Force 51 Figure 3.20 Assigning Secant Stiffness 52 Figure 3.21 Moment-Rotation Relationship for Plastic Hinge 54 Figure 3.22 Define Plastic Hinge Property 57 Figure 3.23 Moment Rotation Data Input 58 Figure 3.24 Define P-M2-M3 Interaction Surface 58 Figure 3.25 Assign Location of Plastic Hinge 59 Figure 3.26 Assigned Hinge in Two-Dimensional Frame 59 Figure 3.27 Assign Frame End Length Offsets 60 Figure 3.28 Assign Joint Constraint as Diaphragm 61 Figure 3.29 Set Load Cases to Run 61 Figure 4.1 Pushover Curve For Three Storey Two-Dimensional Precast Structural Frame 65 with Rigid Beam-Column Connections Figure 4.2 Pushover Curve for Three Storey Two-Dimensional Precast Structural Frame 66 with Semi-Rigid Beam-Column Connections Figure 4.3 Pushover Curve for Three Storey Two-Dimensional Precast Structural Frame 67 with Pinned Beam-Column Connections Figure 4.4 Comparison of Pushover Curves from Three Different Types of Beam- Column Connection Used 68 IX

16 Figure 4.5 Bending Moment Diagram at Near Collapse State for Frame Model with 69 Rigid Beam-Column Connections Figure 4.6 Bending Moment Diagram at Near Collapse State for Frame Model with Semi 69 Rigid Beam-Column Connections Figure 4.7 Bending Moment Diagram at Near Collapse State for Frame Model with 69 Pinned Beam-Column Connections Figure 4.8 Stress-Strain Relationship for Concrete 71 Figure 4.9 Energy-Dissipating Mechanisms for Multi-Storey Frames (Top) and Response 72 Curves for Ductile and Non-Ductile Behavior (Bottom) Figure 4.10 Capacity-Demand Curve for Three Storey Two-Dimensional Precast 74 Structural Frame with Rigid Beam-Column Connections Figure 4.11 Capacity-Demand Curve for Three Storey Two Dimensional Precast 75 Structural Frame with Semi-Rigid Beam-Column Connections Figure 4.12 Capacity-Demand Curve for Three Storey Two Dimensional Precast 76 Structural Frame with Pinned Beam-Column Connections Figure 4.13 Comparison of Capacity-Demand Curves from Three Types of Beam-Column 77 Connection Used Figure 4.14 Immediate Occupancy (Step 4) for Frame Model with Rigid Beam-Column 80 Connections Figure 4.15 Life Safety and Collapse Prevention (Step 5) for Frame Model with Rigid 80 Beam-Column Connections Figure 4.16 Immediate Occupancy and Life Safety (Step 3) for Frame Model with Semi 81 Rigid Beam-Column Connections Figure 4.17 Collapse Prevention (Step 4) for Frame Model with Semi Rigid Beam- 81 Column Connections Figure 4.18 Immediate Occupancy (Step 5) for Frame Model with Pinned Beam-Column 82 Connections Figure 4.19 Life Safety (Step 6) for Frame Model with Pinned Beam-Column Connections 82 X

17 Figure 4.20 Collapse Prevention (Step 8) for Frame Model with Pinned Beam-Column 82 Connections Figure 4.21 Soft Storey Mechanism in Building Failure in Yogyakarta, Indonesia 86 XI

18 LIST OF TABLES List Page Table 2.1 Types of Connections in Precast Frame 13 Table 2.2 Comparison between Rigid, Semi-Rigid and Pinned Connections 17 Table 2.3 Classification System for Semi-Rigid Design in Precast Concrete Frames 27 Table 3.1 Calculated Secant Stiffness and Verified Moment Obtained by SAP Table 3.2 List of Parameters for Three-Storey Two-Dimensional Precast Concrete 43 Skeletal Frame Table 3.3 Beam s and Column s Properties 46 Table 3.4 Calculated Secant Stiffness 52 Table 3.5 Calculated Hinge Length and Location of Hinge 53 Table 3.6 Moment-Rotation Relationship for Three-Storey Two-Dimensional Precast Concrete Frame 56 Table 3.7 Normalized Moment-Rotation Relationship for SAP2000 Input 56 Table 4.1 Ductility Ratio 70 Table 4.2 Performance Points of Precast Concrete Frames with Three Different Types of Beam-Column Connection Used 78 Table 4.3 Performance Levels and Its Damage and Indication Color 80 Table 4.4 Steps at which Limit States IO, LS and CP of Plastic Hinges are Reached and Corresponding Values on Pushover Curve 83 XII

19 CHAPTER 1 INTRODUCTION 1.1 Introduction Precast concrete structure is well-known as a part of the Industrialized Building System (IBS). The building structure is constructed by using massive fabricated construction components. These construction components are fabricated in a factory by casting concrete using few reusable formworks. Then, they undergo curing stage under a controlled environment. When they are ready, they are transported to the construction site and erected as a structure (Glass, 2000). Precast concrete has been used in the United State before the 19 th century. However, it is not widely spread around the world by then. After World War in Europe, it starts to gain popularity as people have to massively reconstruct buildings. During 1901 to 1940, many experiments were done. Since then, large number of commercial offices, hotels, apartments, car parks and factories have been built in Europe and North America (Glass, 2000). There are several advantages of using precast concrete construction. Precast concrete products are high in quality and uniform standard as they are mass produced under a controlled 1

20 environment in a manufacturing plant. Even though the precast components have difficulty in transporting due to heavy and large-sized, the speed of installation is more reliable compared to the cast in-situ concrete. All precast components are designed for simple connection to allow many components to be installed in a short time (Frank, 2002). However, there are some disadvantages of precast concrete construction in term of design and dimension flexibility and also other factors. Design and dimension flexibility may be limited as the manufacturers have fixed sizes and shapes of mould for producing precast components. Besides, the connections that are joining the precast components can be the weakness to the building stability. Hence, these connections are the one of critical design parameters (Mishra, 2011). The design of joints for the beam-column connection is very vital for earthquake resistant of modern structural buildings such as reinforced concrete, steel, and precast concrete buildings. The importance of beam-column connection is recognized for the structural integrity as such beam-column connection is necessary to be capable to resist and sustain the loads transmitted from beams and columns with sufficient stiffness and strength. Moreover, different types of beam-column connection have various characteristics that may influence the behavior of a structure in terms of deflection or bending moment transferred especially in response to earthquake. For example, normal reinforced concrete building has rigid beam-column connections as the building is casted monolithically. These rigid beam-column connections allow the building to be stiff to resist the low lateral force due to low magnitude earthquake and thus, the building will sway at very small displacement. However, when the building meets high magnitude earthquake, 2

21 the building will sway more but due to stiffness of building, structural members will break as the bending moment exceeds the capacity of structural members. 1.2 Problem Statement An earthquake is described as ground shaking caused by the sudden release of energy in the Earth s crust. This energy may be due to different sources, such as dislocations of the crust, volcanic eruptions, or even by man - made explosions or the collapse of underground cavities, such as mines or karsts. In early 19 th century, many studies on predicting earthquake had been tried but been concluded as the earthquake was unpredictable. Later in 20 th century, a few studies finally showed the earthquake is predictable. However, the accuracy of predicting time of occurrence, location of epicenter and magnitude still requires improvement. It is only accurate for predicting the earthquake that is soon to occur. Importantly, earthquake is one of destructive natural disasters that causes building destruction and life lost. Higher the magnitude of earthquake can induce greater ground motion and more energy released. Greater energy released from earthquake is indicating greater destructive power of the earthquake. Kobe Earthquake in 1995 with magnitude 7.2 caused over 10,000 building damaged. A part of them were reinforced concrete buildings which faced shear failure of columns that caused entire structural failure (Figure 1.1). Furthermore, currently important issue to be concerned is that Malaysia has been affected by aftershock from Sumatra s earthquake for several times. 3

22 The survivability of a structural building through an earthquake mainly depends on its earthquake response controlling parameters such as stiffness, strength and ductility. The higher the magnitude of the earthquake can cause the structural building swaying in large deformation or displacement. In the study of structural stability of precast concrete structures, the beam-column connection is the main element governing the structural behavior in responding to various loads such as earthquake. Different types of connections that are available for precast concrete structural building, namely pinned and rigid beam-column connections may provide various stiffness and ductility. The recent studies on precast concrete beam-column connections are mainly in experimental stage. Therefore, these researches are contributing to further exploration on studying the precast concrete structures in seismic zone. Thus, the type of beam-column connection and its design that allows the structure to be more sustainable in seismic zone will be determined. Different type of beam-column connection has different bending moment stiffness. The bending moment stiffness can control the amount of induced bending moment being transferred among structural members of a precast concrete skeletal frame. Consequently, it will affect the deflection behavior of structural members. Large deformation of structural building in response to earthquake can be reduced by increasing the stiffness of its frames at the same it reduces ductility of frames. However, capacity of structural members is easily achieved to limit as less energy released from earthquake losing through small displacement. High ductility may allow the structural building swaying too much in displacement. However, the capacity of structural members is not easily achieved as most of energy from earthquake losing through large displacement. 4

23 Figure 1.1: A collapsed building in Japan s 1995 Kobe Earthquake (Live Science, 2013) 1.3 Significance of Study As recently increasing occurrence of earthquake in Sumatra, the west coast of Peninsula Malaysia begins to frequently feel the effects of earthquake such as tsunami and aftershock. It is notable that since past 30 years, Sabah, a state in Malaysia, has experienced several earthquakes with magnitude of 4.5 to 6.2. Hence, in future, Malaysia might be experiencing more frequent of low magnitude to medium magnitude of earthquakes. More buildings will be structurally damaged and more human lives will be lost due to earthquake. Recently the Malaysia government has begun to promote the use of precast concrete in construction by targeting at least 30% of usage in a construction project and 70% in government 5

24 buildings. As many believe that Malaysia is free from earthquake, precast concrete structures that have been built and will be built are designed without properly resisting the forces from low magnitude earthquake. A structure without proper prevention is prone to be damaged when the earthquake occurs. As the safety of occupants of the structural building is an important concern in the structural design, the analysis of the precast building such as hospitals in earthquake situations must be conducted. It is to prevent important building from being badly damaged when the earthquake suddenly occurs in Malaysia. Hence, it is also to reduce loss of lives in the earthquake area as the precast concrete structures are able to sustain higher magnitude of earthquake. The current Malaysia s building code has not considered earthquake in its code provision. The existing Malaysian buildings and future buildings need to have structural performance to be assessed for its ability to withstand an earthquake s aftershock. Thus, this study can provide important insight which can be useful in future design of Malaysian buildings to reduce threat of earthquake. Furthermore, the life safety of building occupants can be ensured by using a structural design that is able to withstand earthquake. 6