A STUDY OF WOOD BASED SHEAR WALLS SHEATHED WITH OVERSIZE ORIENTED STRAND BOARD PANELS by MING HE B.Eng., Beijing University of Iron and Steel Technology, 1982 M.Eng., The University of Science and Technology Beijing, 1988 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in FACULTY OF GRADUATE STUDIES Department of Wood Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March, 1997 ©Ming He, 1997 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of JAjiftt-dL The University of British Columbia Vancouver, Canada Date M-AA^cJs 14, / <? 9 ^ DE-6 (2/88) ABSTRACT A new wood based shear wall system built with nonstandard large dimension oriented strand board panels has been developed. The project described in this thesis consists of studies to 1) experimentally investigate and quantify the structural performance of the new shear wall system under monotonic and cyclic lateral loading conditions, considering different types and spacings of panel-frame nail connectors, and 2) analytically predict and model the performance of the new shear wall system. A test facility has been built for full scale shear walls of up to 2.4 x 7.3 m in dimension where both lateral and vertical loads can be applied simultaneously onto the wall assembly. The experimental program has been divided into a static and a cyclic test phase. Thirteen shear wall systems with standard 1.2 x 2.4 m and with oversize panels have been tested to investigate the influence of 1) panel size, 2) panel-frame nail connector type, 3) panel-frame nail connector spacing, and 4) cyclic loading protocol on the overall shear wall behaviour. A database on the structural performance of wood based shear walls sheathed with oversize oriented strand board panels has been generated. The database includes information on strength, stiffness and ductility properties, energy dissipation and failure modes of shear walls under different testing conditions. A substantial increase in both stiffness and lateral load carrying capacity was achieved by shear walls built with oversize panels as compared to standard panels. A further reduction in nail spacing around the perimeter of the full size panel increased the lateral load resistance to more than double that of regular walls. The failure modes in the shear walls were shown to be substantially different under monotonic and currently used cyclic test conditions. The former was mainly nail withdrawal while the latter was dominated by low cycle nail fatigue failures. A new cyclic loading protocol was proposed and tested, which resulted in failure modes similar to those observed in dynamic earthquake tests. In examining the dissipated energy as the area under the ii load deformation curve, it seems that the walls built with the standard panels can dissipate more energy under cyclic loading, compared to the walls built with oversize panels. Furthermore, a group of tests has been conducted to investigate the load-slip characteristics of panel-frame connectors. A nonlinear finite element analysis program has been adopted to predict and model the performance of shear walls built with oversize panels. The program results had good agreement with the initial part of the nonlinear behaviour of the shear walls in the tests, which is before the panel- frame connectors failed. It could not, however, follow the test results when the connectors failed and further refinements to the program have been suggested to incorporate nail failure occurrence. iii TABLE OF CONTENTS ABSTRACT ii TABLE OF CONTENTS iv LIST OF TABLES vii LIST OF FIGURES viii LIST OF PHOTOGRAPHS xi ACKNOWLEDGMENT xii 1. INTRODUCTION 1 2. BACKGROUND 5 2.1. Structures and roles of wood based shear walls 5 2.2. Historical review 6 2.3. Structural analysis models for walls under monotonic loading conditions 8 2.3.1. Tuomi and McCutcheon's model 8 2.3.2. Easley et a/.'s model 9 2.3.3. Gupta and Kuo's model 10 2.3.4. Foschi's model 11 2.4. The cyclic testing protocols used in shear wall studies 11 2.4.1. ASTM protocol 14 2.4.2. CEN protocol 15 2.4.3. FCC-Forintek protocol 16 2.5. Effect of shear wall geometric configurations 17 2.6. Oriented strand board (OSB) 18 3. THE SHEAR WALL MODEL AND ANALYTICAL PROGRAM 19 3.1. The shear wall model 19 iv 3.2. Panel members 20 3.2.1. Formulation of the panel finite elements based on the principle of potential energy 20 3.2.2. Shape functions 22 3.2.3. Numerical integration 25 3.3. Frame members 25 3.4. Panel-frame connections 27 3.5. The frame-frame connections 29 3.6. The flow chart of Diaphragm Analysis Program 31 4. EXPERIMENTAL PROCEDURES 33 4.1. Experimental facilities 33 4.2. Test shear wall configurations 37 4.3. Test program 40 4.4. Loading Scheme 41 4.4.1. The monotonic loading scheme 41 4.4.2. The Forintek cyclic loading scheme 41 4.4.3. The CEN Short cyclic loading scheme 43 4.4.4. A newly proposed cyclic loading scheme 43 5. EXPERIMENTAL RESULTS 45 5.1. Experimental results on wall performance 45 5.2. Discussion of shear wall tests under monotonic loading conditions 46 5.3. Discussions of the shear wall tests under cyclic loading conditions 53 5.3.1. Performance of shear walls with different configurations 54 5.3.2. Comparison among cyclic loading schedules 62 5.3.3. Energy Dissipation 66 6. THE STATIC NAIL TESTS 73 v 6.1. Description of static nail tests 73 6.2. Test results 75 6.2.1. The types of nails 77 6.2.2. The lumber orientation 78 6.2.3. Nail spacing and number of nails 78 6.2.4. Conditioning duration 78 6.2.5. Failure modes 79 6.3. The parameters for the panel-frame nail connection and numerical examples 79 7. CONCLUSIONS 84 8. BIBLIOGRAPHY 86 9. APPENDIX 1. SUPPLEMENTARY INFORMATION OF THE STATIC NAIL TESTS 90 9.1. Nail test specimens 90 9.2. Parameters for nail load-slip models in shear wall studies 90 9.3. Influence of nail load-slip parameters variation on DAP 91 VI LIST OF TABLES Table 4.1 Shear wall test program 41 Table 4.2 The parameters in cyclic tests using Forintek cyclic test protocol 42 Table 4.3 Displacement amplitude schedule of various cycle groups as a percentage of Ayieid. 42 Table 4.4 The parameters in the cyclic test using CEN Short cyclic test protocol 43 Table 4.5 The parameters used in cyclic test of shear wall 13 44 Table 5.1 Summary of shear wall test results (refer to Table 4.1 for wall configurations) 46 Table 5.2 Major test results for shear walls under monotonic loading conditions 47 Table 5.3 Major test results for shear walls under cyclic loading conditions 54 Table 5.4 Degradation of load capacity occurring in cycles 65 Table 5.5 Dissipated energy in shear wall during cyclic loading. 67 Table 5.6 Energy dissipation in shear walls 12 and 13 under cyclic loading 71 Table 6.1 The configurations of specimens 74 Table 6.2 Summary of results in static nail tests 77 Table 6.3 The parameters for both spiral nail and common nail 79 Table 6.4 Comparison of the peak loads from the test and numerical analysis 83 Table 9.1 The parameters required by nail load-slip model in DAP 91 Table 9.2 The materials of nail test specimens 91 Table 9.3 Variations in E0 and P\ 94 vii LIST OF FIGURES Figure 2.1 Tuomi and McCutcheon's model 8 Figure 2.2 Easley et aPs model and assumed pattern of sheathing fastener forces 9 Figure 2.3 Gupta and Kuo's model 10 Figure 2.4 Load-slip property of connectors in Foschi's model 11 Figure 2.5 ASTM loading history 14 Figure 2.6 Definition of yield and ultimate displacement in different protocols - 15 Figure 2.7 CEN protocol: (a) CEN Long; (b) CEN Short 15 Figure 2.8 FCC-Forintek protocol 16 Figure 3.1 Shear wall model 19 Figure 3.2 Panel finite element 23 Figure 3.3 The locations of the Gauss points 25 Figure 3.4 Frame element 25 Figure 3.5 The deformation of panel-frame connection 27 Figure 3.6 The nail load-slip relationship 29 Figure 3.7 The frame-frame connection 29 Figure 3.8 DAP main flow chart 31 Figure 3.9 The flow chart of SADT 32 Figure 4.1 The scheme of the shear wall test setup assembly 34 Figure 4.2 The test control and data acquisition system 36 Figure 4.3 The panel layouts 38 Figure 4.4 The cyclic schedule for wall 13 44 Figure 5.1 Load-displacement curves for shear walls 1, 2 and 7 47 Figure 5.2 Load-displacement curves for shear walls 2, 8 and 10 49 viii Figure 5.3 Load-displacement curves for shear walls 2 and 5 53 Figure 5.4 Cyclic load-displacement curve and static envelope for wall 3 55 Figure 5.5 Cyclic load-displacement curve and static envelope for wall 4 55 Figure 5.6 Cyclic load-displacement curve and static envelope for wall 9 56 Figure 5.7 Cyclic load-displacement curve and static envelope for wall 11 56 Figure 5.8 The distributions of failed nails along the height of wall 57 Figure 5.9 Cyclic load-displacement curve and static envelope for wall 6 58 Figure 5.10 The comparison of joints deflection in wall 12 59 Figure 5.11 The comparison of joints deflection in wall 13 59 Figure 5.12 Cyclic load-displacement curve and static envelope for wall 12 63 Figure 5.13 Cyclic load-displacement curve and static