Learning from Local Wisdom: Friction Damper in Traditional Building

Indonesia is situated in the so called “Ring of Fire” where earthquake are very frequent. Despite of all the engineering effort, due to the March 28, 2005 strong earthquake (8.7 on Richter scale) a lot of modern buildings in Nias collapsed, while the traditional Northern Nias house (omohada) survived without any damage. Undoubtedly many other traditional buildings in other area in Indonesia have survived similar earthquake. Something in common of the traditional building are the columns which usually are not fixed on the ground, but rest on top of flat stones. In this paper some traditional building are subjected to non linear time history analysis to artificial earthquake equivalent to 500 years return period earthquake. This study shows that apparently the columns which rest on top of flat stone acts as friction damper or base isolation. The presence of sliding at the friction type support significantly reduces the internal forces in the structure

Seismic Performance of a Three-Story Reinforced Concrete Building with Masonry Infill Walls and Friction Base Support

The stiffness of masonry infill walls is commonly neglected in design practice of Reinforced Concrete (RC) structures. In fact, the stiffness of masonry infill wall may significantly influence seismic performance and dynamic behavior of RC buildings. In this research, influence of masonry infill walls to the structural performance of a three-story RC frame is investigated. In addition, possible application of friction-based support is also studied. Full 3D non-linear time history analysis is conducted to observe the behavior of the structure under two-directional ground motion. In the analysis, any failed elements are removed subsequently from the model to avoid numerical analysis problem. The result shows that the masonry infill walls can significantly influence the structural behavior of RC structure. Inappropriate placement of masonry wall may lead the building undergo soft-story mechanism. It is also found that the use of friction-based support can effectively improve the seismic performance of the building

Performance of Six- and Ten-story Reinforced Concrete Buildings Designed by using Modified Partial Capacity Design (M-PCD) Method with 70% Shear Force Ratio

One design alternative of earthquake resistant building is Partial Capacity Design (PCD) method. Unlike the commonly used capacity design method, PCD allows a safe failure mechanism which is called partial sidesway mechanism. In this mechanism, all beams and some columns are allowed to experience plastic damages while some selected columns are designed to remain elastic (called elastic columns). A new approach to predict the required strengths needed to design each structural member, called modified-PCD (M-PCD) is proposed. In this research six�and ten-story reinforced concrete buildings were designed using M-PCD, and their seismic performances are investigated. The base shear force resisted by the elastic columns was set to approximately 70% of the total base shear. Both nonlinear static procedure (NSP) and nonlinear dynamic procedure (NDP) are used to analyze the structures. The results show that the expected partial side sway mechanism is observed, and the drifts of the buildings are acceptable

Behavior of Reinforced Concrete Columns Retrofitted by External Steel Angle Collars under Axial Compression and Combined Axial Compression and Reversed Cyclic Loading

In reinforced concrete (RC) buildings, damages in columns should be avoided during the earthquakes since they have less ductile inelastic behavior which can lead to proggressive damages and collapse of the structure. Researchers have developed several retrofitting techniques to improve the performance or ductility of RC columns. Concrete jacketing, steel jacketing, external strand prestressing, Fiber Reinforced Polymer (FRP) jacketing, and steel collar jacketing to name a few are among the developed retrofit approaches. In this study, a new retrofitting technique utilizing steel collars as external confinement is proposed. The aim of the study is to develop an effective, yet economical, and practical method to retrofit square, and rectangular, or even elongated RC column sections. Steel angle or L-shapep sections were used as collar elements, which were mounted externally at spacing surrounding the perimeter of the column to enhance the column’s strength, particularly its ductility. To achieve this objective, two phases of experimental program were carried out. In the first phase of the experimental program, fourteen concrete column specimens were built and tested under monotonic axial compressive load in order to study the impact of the proposed external retrofitting method to the strength and most importantly to the ductility enhancement of the columns. To study this effect, volumetric ratio of confining elements was set as the main parameter. Some stiffening techniques of the collars were also investigated to further examine the potential of the proposed method. The results indicated that the strength, and strain ductility of the retrofitted specimens were enhanced. An analytical model to predict the actual stress-strain curve of the columns confined by external steel angle collars was developed and verified against the experimental stress-strain data. The predictions were in good agreement with the experimental results. The peak stress, strain at peak stress and strains at 50 and 80 percent of the peak stress can be predictied reasonably well. A proposed calculation procedure for retrofit work is also introduced. It provides the need of additional external steel collars in order to meet the target of the column’s strength. The idea is to combine the confining stresses provided by internal confinement and external steel collars by taking the average proportionally to the influenced area. Comparisons with experimental data indicated that the proposed approach can predict with reasonable margins on the conservative side. In the second phase, five concrete column specimens were cast, and tested under combined axial compression, and quasi-static reversed cyclic lateral load. These tests were intended to investigate the performance of the retrofitted specimens under simulated earthquake load. The enhancement of strength, and ductility which lead to larger energy dissipation capacity are clearly identified. The acceptance criteria set by ACI 374.1-05 is also satisfied. Additionally, a proposed design procedure is also developed based on the limited data obtained from the second phase of the experimental program. The step-by-step design procedure accommodates the need of additional external steel angle collars to retrofit the existing column to improve its ductility. In conclusion, the proposed retrofitting method can be applied as an alternative solution on rehabilitation of seismically deficient square RC columns. ====================================================================================== Pada bangunan beton bertulang (BB), kerusakan kolom sebaiknya dihindari saat gempa karena perilaku in-elastis yang kurang daktail pada kolom dapat menyebabkan kerusakan progresif, dan keruntuhan struktur. Para peneliti telah mengembangkan banyak teknik retrofit untuk memperbaiki kinerja atau daktilitas kolom BB. Pembesaran penampang beton, penambahan baja lembaran / cincin, stran eksternal prategang, Fiber Reinforced Polymer (FRP), dan sabuk baja merupakan beberapa metode retrofit yang dikembangkan. Pada penelitian ini, diusulkan sebuah teknik baru menggunakan sabuk baja sebagai pengekang eksternal. Tujuan dari penelitian ini adalah untuk mengembangkan metode retrofit untuk kolom BB bujursangkar, atau bahkan persegi panjang yang efektif, tapi ekonomis, dan praktis / mudah dilaksanakan. Profil baja siku atau L digunakan sebagai elemen sabuk, yang diaplikasikan secara eksternal mengelilingi keliling kolom BB dengan spasi tertentu untuk meningkatkan kekuatan, dan daktilitasnya. Untuk mencapai tujuan ini, dua fase ekperimen dilakukan. Pada fase pertama dari eksperimen, empat belas spesimen kolom beton dibuat dan, diuji tekan monotonik untuk menyelidiki pengaruh dari metode retrofit eksternal yang diusulkan pada peningkatan kekuatan, dan lebih penting lagi, terhadap peningkatan daktilitas dari kolom. Untuk mempelajari efek ini, rasio volumetrik dari elemen pengekang digunakan sebagai parameter utamanya. Beberapa teknik pengakuan sabuk baja juga dilakukan, untuk menyelidiki lebih jauh potensi dari metode ini. Hasil menunjukkan adanya peningkatkan kekuatan, dan daktilitas dari spesimen yang diretrofit. Sebuah metode analitis untuk memprediksi kurva hubungan tegangan-regangan aktual dari kolom yang dikekang secara eksternal oleh sabuk baja, dikembangkan dan diverifikasi terhadap data tegangan-regangan dari eksperimen. Hasil menunjukkan prediksi yang baik. Tegangan puncak, regangan pada regangan puncak, dan reganganregangan pada 50 dan 80 persen tegangan puncak dapat diprediksi dengan baik. Sebuah prosedur perhitungan untuk pekerjaan retrofit juga diperkenalkan. Prosedur ini memberikan kebutuhan dari tambahan sabuk baja eksternal untuk memenuhi target kekuatan kolom. Idenya adalah dengan mengkombinasikan tegangan-tegangan kekang yang disumbangkan oleh pengekang internal maupun eksternal dengan merata-ratakan nilainya secara proposional terhadap daerah yang dipengaruhi masing-masing. Perbandingan dengan data eksperimen mengindikasikan bahwa pendekatan yang diusulkan dapat memprediksi dengan marjin yang baik pada kecenderungan yang konservatif. Pada fase kedua, lima spesimen kolom beton dibuat dan diuji dengan kombinasi beban aksial dan lateral siklik bolak-balik quasi-static. Uji ini dilakukan untuk menyelidiki kinerja spesimen yang diretrofit terhadap simulasi beban gempa. Peningkatan kekuatan dan daktilitas yang berujung pada lebih besarnya kapasistas disipasi energi terlihat dengan jelas. Kriteria penerimaan dari ACI 374.1-05 juga terpenuhi. Sebagai tambahan, prosedur perencanaan juga dikembangkan berdasarkan data terbatas yang diperoleh dari eksperimen fase kedua. Prosedur perencanan langkah demi langkah mengakomodasi kebutuhan tambahan sabuk siku baja eksternal dalam meretrofit kolom untuk meningkatkan daktilitasnya. Pada akhirnya, dapat disimpulkan bahwa metode retrofit yang diusulkan dapat dipakai sebagai solusi alternatif pada rehabilitasi kolom BB yang tidak memenuhi persyaratan gempa

Application of modified partial capacity design on six-story Lshaped reinforced concrete buildings with variations on elastic columns configurations

Modified Partial Capacity Design (M-PCD) is an alternative design method for seismic-resistant structures. M-PCD adopts the partial side sway mechanism for its failure mechanism where beams and some columns are allowed to develop plastic hinges. This method uses two models for design. The first model simulates a small earthquake occurrence and is used to design beams and plastic columns. The second model simulates a larger earthquake occurrence and damages on the structure. The elastic columns are designed based on the superposition of internal forces from the first and second models, provided that the effects from gravity loads are considered only once. This study focuses on the application of M-PCD on six-story L-shaped reinforced concrete buildings with variations on elastic columns configurations. Nonlinear time history analyses are used to determine the buildings’ performance on two earthquake levels (EDRS and MCER) and two earthquake directions (0° and 45° rotated earthquake). The results show that the partial side sway mechanism is observed in most of the analyzed structures and drifts are within set boundaries

Application of Soil Structure Interaction on Building with Basement using Nonlinear Soil Springs

In a typical building design, the interaction between building and surrounding soils is often ignored. Since soil is deformable and has limited capacity to resist loads, this interaction, called soil-structure interaction (SSI), could alter building responses, especially during earthquake loadings for buildings with significant basement depths. In this study, a 10-story reinforced concrete building with 3-level basement was used to evaluate the effects of SSI on building during earthquakes. Dynamic time response analyses were performed using earthquake time histories scaled to a design response spectrum for a Surabaya, Indonesia, location. Soil responses during earthquakes were modeled using nonlinear hysteresis normal and elastic-perfectly plastic frictional soil springs, developed using the hardening soil with small strain stiffness model. Depthvarying ground motions were also applied along the basement depth. The results show inconclusive SSI effects, where some of the time histories produce greater base shears and interstory drifts when SSI is considered, while others show the opposite results

Application of Modified-Partial Capacity Design Method on 6- and 15-story Square Buildings with Variation in number of Elastic Columns

Modified-Partial Capacity Design (M-PCD) is proposed as one alternative of structural design methods. In M-PCD, the partial side sway mechanism where beams and some columns may develop plastic hinges. This method uses two structural models during the design process. The models are used to simulate undamaged and damaged structures when subjected to design earthquake (R=8.0) and larger target earthquake (R=1.6) respectively. In this study, 6- and 15- story square buildings with 30% and 50% elastic column are designed using M-PCD. Performances of the buildings are investigated by using non-linear time history analysis. Results show that the buildings� performances are still unsatisfactory, especially for the 15-story buildings. However, it should be noted that the levels of earthquakes used for the analysis were larger than that used for the design. A more accurate prediction of the required strength should be developed further to improve M-PCD

Flexural and Shear Behavior of 3D Printed Reinforced Concrete Beams: An Experimental Study

3D Concrete Printing (3DCP) provides many advantages for construction industry especially on productivity, waste, labor, and environment. Many researches have been conducted on the material development for 3DCP. However, there are not many researches which study the structural behavior of 3DCP. This experimental research aims to analyze flexural and shear behavior of 3D printed reinforced concrete beams. Five longitudinal reinforcement ratios were used to analyze crack patterns, failure mode, ductility, and capacity of those beams. The experimental results were then compared with analytical results by using ACI design code. The results show that higher longitudinal reinforcement ratio yields higher flexural and shear capacity of 3DCP beams. Due to layer-by-layer printing process, 3DCP beams are prone to local failure of filaments. Placement of longitudinal reinforcement might initiate macroscopic voids which could cause slippage and sudden drop on the capacity. Furthermore, ACI code underestimates the capacity of 3DCP beams failing in shear by some margins

Review on 3D printed concrete as structural beam members

Recently, Three-Dimensional Concrete Printing (3DCP) has gained its popularity as construction material. It offers several advantages over conventionally casted concrete such as absence of formwork, reduction of construction equipment transportation, greater safety, reduction of labour cost, and many others. However, the technology also comes with many challenges. Researches in this area can be classified into two issues which are fresh and hardened states of the printed concrete. Investigation of fresh concrete focuses on the optimal design of rheological properties which determines the pumpability, extrudability, and buildability. While mechanical properties of hardened 3DCP are usually investigated by adopting standard tests for conventionally casted concrete. However, due to the complexity of printing process, it is often that 3DCP behaviours cannot be predicted by its mechanical properties obtained from the tests. This paper reviews some studies done by others to highlight potential manufacturing process related weak points of 3DCP as structural beam members

Performance of square reinforced concrete columns externally confined by steel angle collars under combined axial and lateral load

Providing good ductility has become research interest in the area of seismic resistant structures. Particularly in Reinforced Concrete (RC) structure, such ductility is commonly achieved by providing good confinement. Confinement can be conventionally provided by internal stirrups, and also additional external elements which are commonly used as strengthening or retrofit works. Attaching external steel collars on concrete columns is one of many techniques in enhancing the ductility. In this study, performance of such retrofitting method is investigated through laboratory experiment. Totally five specimens are built for this investigation. The first two specimens (CS1-1, and CS1-2) are control specimens, which are conventionally confined by stirrups. The other three specimens (S1-3, S1-4, and S1-5) are only confined externally with the steel angle collars. All five specimens are tested under combined axial and lateral load. The axial load is kept constant at 30% of plain concrete axial capacity to model the gravity load. The lateral load given is according to ACI 374.1-05 quasi-static cyclic loading protocol. Lateral load resistance is recorded throughout the cyclic loading, and plotted against the corresponding lateral displacement. Results show that specimens with smaller volumetric ratio of confining element suffered brittle failure (poor ductility). Specimens with adequate confinement show good deformability and ductile failure. In conclusion, the retrofitting method by providing external steel angle collars is very promising