A New Nonlinear Three Dimensional Finite Element For Curved Beams

A new nonlinear geometric curved-beam finite element is developed for three dimensional space systems by using the principal of potential energy and polynomial functions. The element is assumed to be curved in one plane only, but deformations in the three-dimensional space is considered. The element geometry is defined by a second order polynomial. In deriving the linear stiffness matrix, k, the displacement functions are approximated by cubic polynomials. In deriving the incremental stiffness matrices, ni and 1,2, however, while the transverse displacements are still approximated by cubic polynomials, the longitudinal displacements and twist are approximated by linear polynomials. A major improvement in the accuracy of the element is obtained by averaging the nonlinear part of the axial strain. The method of solution used is that of the fixed Lagrange coordinates and the NewtonRaphson procedure. Comparisons of numerical results with those of various other methods indicate that, in terms of the number of elements or degrees of freedom needed for convergence, the method seems significantly more effective than most. Non of the others seen to be more effective. The problems considered included shallow and deep arches, extremely thin arches, and arches of various profiles

Pengaruh Pukulan Hammer Saat PemancanganDalam Mendukung Gaya Gempa Horisontal

In earthquake regions, like Indonesia, pile foundation system has additional main function to resist lateral dynamic loading induced by earthquake. Since the piles commonly fall into the category of "long pile", their first cracking moment and ultimate flexural capacity become important parameters in design. This research was conducted to prove experimentally the effects of driving hammer during construction phase on the degradation of the first cracking moment and ultimate flexural capacity of the non-prestressed precast , concrete piles. Twelve non-prestressed precast concrete piles, that experienced various number of real drop hammer blows (0 upto 512 blows), were taken from site and tested in the laboratory. The piles had triangle cross sectional shape, three q5 19 nun steel reinforcing bars, and made of concrete with f MPa. The piles were devided into 4 groups: K1 (control group) for piles that had not been experiencing any blows\u27 K2 for thOse experiencing 142-165 blows, K3 for 240345 blows, and K4 for 512 blows. FourLpoint-loading procedure was adopted for testing the piles flexurally, and their load-deflection curve responses were observed and recorded. The loads were applied ,sequently with the load increment of 10 kN upto the\u27collapse. The results showed that compared relatively to K1: (a): K2, K3and K4 experiencing 22.6%, 41.9%, and 63.88% degradation of the first cracking moments, respectively(b) the degradation of the first cracking moment tends to increase with the increase of the number of hammer blows, however (c) the degradation of the flexural stiffness, yield moment, ultimate moment, and displacement ductility of the non-prestressed precast concrete piles did not seem to be significant. The results suggested that driving precast piles using drop hammer did not alter the flexural properties of the driven piles significantly

Analisis Buckling Pada Struktur Dengan Finite Element Method

ABSTRAK: Dalam paper ini, beban kritis struktur akibat elastic buckling dianalisis dengan Finite Element Method. Elemen beam-column diturunkan berdasarkan polinomial tinier untuk longitudinal displacement, dan polinomial berderajat tiga untuk transverse displacement. Nonlineartiy timbul karena the second order term dalam persamaan strain-displacement tidak diabaikan, sehingga nan¬tinya persamaan kesetimbangan struktur dapat ditulis berdasarkan the deflected geometry. Matriks kekakuan elemen yang diperoleh terdiri dari bagian yang linier, 1k,, j, dan bagian yang nonlinier, [nil dan Matriks [nil dan M2] berturut-turut adalah fungsi linier dan kuadrat dari displacements. Persamaan kesetimbangan incremental dari struktur, yang dalam hal ini nonlinier, diperoleh dari variasi kedua terhadap energi potensial struktur. Dengan memakai prinsip bahwa vektor beban incremental menjadi not pada saat terjadi buckling, maka persoalan analisis beban kritis struktur akibat elastic buckling dapat diformulasikan sebagai persoalan eigenvalue. Untuk solusi quadratic eigenvalue dipakai the determinant search method, sedangkan untuk solusi linear eigenvalue dipakai the inverse vector iteration technique. Dari contoh-contoh numerik dapat disimpulkan bahwa beban kritis yang diperoleh dengan prosedur ini cukup akurat untuk keadaan dimana prebuckling displacement dari struktur yang ditinjau cukup kecil. Untuk kondisi yang sangat umum, beban kritis tersebut dapat diperoleh dari kurva beban-lendutan yang merupakan solusi dari nonlinear equilibrium equations. Keywords: buckling, kurva beban lenduta

PENGARUH PENAMBAHAN FIBER LOKAL PADA PERILAKU TORSI KOLOM BETON BERTULANG PENAMPANG LINGKARAN DENGAN TULANGAN SPIRAL (THE EFFECT OF LOCAL FIBER ON THE TORSIONAL OF SPIRALLY CIRCULAR REINFORCED CONCRETE COLUMNS)

ABSTRACT Columns are structural element, which are dominantly axially loaded. However sometimes columns are laterally loaded by shear, bending, and torsion. In order to make column have high ductility, can be added by fiber material. The aim of the research is to find the effect of local fiber on the behavior of circular torsion concrete column with spirally reinforcement. This research is held on 6 (six) columns, three of them are normal concrete columns and the others are fiber concrete columns. The circular columns have 200 mm diameter and 950 mm length. The columns are fixed on rigid floor. The ratio of longitudinal reinforcement each column is 2,08 % and ratio of spiral reinforcement 1,45 %. The local fiber is one percent, with aspect ratio (lid) 60. Every column is loaded under constant effectiv axial load 210,186 kN and cyclic torsion until failure. The result of the research shows that with 1 % local fiber the tension strength (splitting) of the fiber concrete increase up to 40,83 %, and the compression strength is almost the same as normal concrete. The strnght of spirally reinforcement are 201,62 Mpa and 163,19 rispec- tively on normal and fiber concrete. The local fiber does not influence on first crack torsion, but increas on ultimit strength of the concrete columns, and ductility of the columns by first crack is increassed 125 %, more than normal concrete columns. The first crack of normal concrete columns experiment are higher then Skew Bending and Space Truss method, 49,81 % and 15,17 % repectively. The first crack of fiberconcrete columns experiment eqaul Skew Bending method, but lower then Space Truss 25,85 %. The ultimate torsion experiment of normal concrete columns are higher then Skew Bending and Space Truss method, 20,57 % and 28,25 % respetively. Tthe ultimate torsion fiber concrete columnsexperiment are higher than Skew Bending 12,02 %, but lower then Space Truss 13,56 %. Before the first crack, the increased angle torsion linear to torsion, and so to be large and collapse. The normal concrete columns spall suddenly, but the fiber concrete columns are not. The spalling area of normal concrete column is larger than fiber concrete column. The stiffnes of fiber concrete column is higher then normal concrete column 7,3 %. Keywords : circular column, spirally reinforcement, torsion, cyclic, fiber concrete, spallin

Plastic collapse load analysis of structures considering Moments and axial force

ABSTRAK A procedure for the analysis of plastic collapse load of structures considering moments and axial forces is presented. The method is developed based on the static or lower bound theorem. Essentially, this approach involves the determination of the largest load factor for which a statically admissible and safe distribution of internal forces exists. In linear programming form, it is equivalent to ma ximizing the load factor subject to the conditions of equilibrium and yield. In this formulation, the displacement method is employed to obtain the internal forces influence coefficients. Those coefficients are used to obtain the sets of statically admissible internal forces. By substituting those forces into the yield surface, which is approximated by piece wise linear functions, the problem of plastic collapse load analysis can be cast into linear programming problem. A linear programming solution algorithm so called Phase I-Phase 2 procedure is used to solve the problem. A computer program was prepared for the implementation of the method and a number of numerical examples involving multistory frames and tied arch bridge structures was also considered. Numerical results indicated that the method developed in the present study is found to be accurate, much simpler than the available methods, and is capable of analysing structures with irregular geometry. Key words: plastics collaps

Finite Element model untuk analisis struktur lengkung tiga dimensi

ABSTRAK Pada penelitian ini finite element model untuk analisis struktur lengkung tiga dimensi telah dikembangkan berdasarkan polinomial berderajad tiga untuk displacement function nya dan polinomial berderajad dua untuk geometri lengkangannya (geometri lengkungan boleti sembarang). Sister koordinat yang dipakai untuk menjabarkan matrix kekakuan elemen lengkung adalah sistem koordinat karvilinier. Matrix kekakuan elemen yang diperoleh berorde 76 x 16 , dengan nodal degrees of freedom terdiri dari bagian yang essential (12 buah) clan bagian yang nonessential (4 buah). Karena kompleksnya fungst-fungsi yang diinâ¢egralkan untuk memperoleh matrix kekakuan elemen, integrasi numeris dengan met ode Gauss quadrature terpaksa ditempah. Selanjutnya derajad kebebasan .yang nonessential dikondensasikan sehingga menghasilkan matrix kekakuan berorde 12 x 12, dengan semua derajad .kebebasan berupa essential degrees of freedom. Dari contoh-contoh numeris (yang telah mencakup berbagai kondisi batas, geometri iengkungan, dan pembebanan), terbukti bahwa finite element model usulan untuk struktur lengkung ini sangat althrat, dan konvergcnsi ke hasil eksaknya juga cepat. Dapat disimpulkan pala bahwa sebagal pedoman praktis dalam menggunakan finite element model usulan ini untuk analisis, cukup diperlukan 4 elemen untuk struktur pelengkung simetris dan 8 elemen untuk struktur pelengkung yang tak simetris (yang geometri lengkungannya sembarang Keywords: geometri lengkangan, finite eleme

PENGARUH SPASI ANTAR LEMBAR PERKUATAN TERHADAP KARAKTERISTIK KEKUATAN PASIR YANG DIPERKUAT = Effects of Reinforcement Fabric Spacing Due to The Strength Characteristics of Reinforced Sand

ABSTRACT The objectives of this research was to study the behavior of Sundak beach sand that reinforced by nonwoven geotextile, and to explore additional knowledge and references on reinforced soil in Indonesia. Many researchers had proved that triaxial compression equipment could be used to study the behavior of reinforced soil by reinforcement fabrics. Conventional triaxial compression tests had been conducted using standard specimen with 70 mm dia. and 147 mm height. Nonwoven polyfelt geotextile was used as reinforcement. Test results were plotted as stress-strain curves and analyzed by Mohr circle and Mohr-Coulomb failure envelope. The results showed that the spacing between reinforcement fabrics affected significantly on the sample strength. Furthermore, uniformity of spacing between reinforcement fabrics was also the important factor that influenced the strength of reinforced sand. Keywords: spacing between reinforcement fabrics, strength, reinforced san

STUDI EXPERIMENTAL BALOK SLOOF-KOLOM PADA RUMAH INSTAN STRUKTUR BAJA DENGAN METODE PEMBEBANAN SIKLIK

Rumah Instan Struktur Baja (RISBA), merupakan model bangunan yang dapat digunakan dalam rekonstruksi perumahan masyarakat yang rusak dilanda gempa di Lombok. Rumah RISBA dipilih karena dari segi bahan yang relatif mudah ditemukan dan terbuat dari bahan ringan, dari segi biaya relatif lebih murah dan dan dari segi waktu konstruksi relatif lebih cepat dibandingkan jenis bangunan lain yang terbuat dari beton. Untuk menentukan resistensi kolom rumah RISBA, studi eksperimental dilakukan pada perilaku siklik kolom (mewakili setengah dari tinggi kolom aktual) 1500 mm yang di sendi pada balok sloof sepanjang 750 mm. Tes siklik dilakukan berdasarkan metode ASTM-E2126. Bahan baja memiliki proerties berikut: fy = 268.104 MPa , dan fu = 331.311 MPa, sedangkan kekuatan kompresi mortar yang digunakan adalah fc' = 9.122 MPa. Loop histeresis yang dihasilkan dan kurva amplop untuk spesimen SB-1 adalah : (a) Ppeak (+) adalah 5,01 kN pada perpindahan 84 mm dengan rasio drift 5,6%, (b) Ppeak (-) adalah 4,93 kN pada perpindahan 84 mm dengan rasio drift 5,6%. Selisih antara SB-1 dan SB-2 pada Ppeak (+) adalah 0,02 kN, sedangkan Ppeak (-) adalah 0,2 kN. Jenis kegagalan pada spesimen SB- 1 adalah dalam bentuk buckling lokal pada kolom, dan kegagalan kompresi pada balok sloof, sementara jenis kegagalan pada spesimen SB-2 adalah dalam bentuk kompresi pada balok sloof tetapi tidak ada kegagalan buckling pada kolom

Analisis Derajat Kerusakan dan Penurunan Modulus Elastisitas Material Cement Treated Base (CTB) menggunakan UPV test dan Concrete Quality Designation (CQD)

Cement-treated base (CTB) is a type of foundation material commonly used in pavement structures which initially has high stiffness, but due to repeated loads CTB tends to experience more cracks which can cause a decrease in its elastic modulus. This study aims to determine the extent of damage and decrease in the value of CTB's elastic modulus before and after cracking through ultrasonic pulse velocity (UPV) test and unconfined compressive strength (UCS) tests on CTB cylinder samples. The CTB material quality index was evaluated using a concrete quality designation (CQD). The results showed that the magnitude of stress applied to  CTB affects the degree of damage, and the degree of damage to CTB significantly affects the material’s modulus of elasticity. The greater the degree of damage to CTB, the smaller the elastic modulus will be. For applied stress with CTB damage level of 32%, the elastic modulus decreases by 33.55%. The level of damage caused by the application of the maximum stress (100%) on CTB sample reached 95.29%, and the modulus of elasticity decreased by 83.30%. The CTB sample with 95.29% degree of damage has the same elastic modulus as the unbound granular aggregate material

Construction Method and Performance of Bugis Traditional House in Wind Disasters

Bugis ethnic in South Sulawesi Province, Indonesia is known as an old tribe who domiciled in the south peninsula of Sulawesi island. They have characteristics of high legacy, culture by the script called lontaraq and life in a traditional stilt house called bola ogi. This house was built in certain methods and become a research problem. The goal of this study is to reveal the construction method and the performance of the Bugis traditional house in facing of wind disaster. The research methods are field observation and in-depth interview. Field observation to reveal the old construction methods of 100 years traditional the Bugis house and its performance in collapse by wind disasters. In-depth interview to strengthen information. The research revealed that Bugis house made of wood and its built-in certain construction methods called mappasituppu. Structure system consists of the main and secondary structure which is joined together rigidly an appropriate hierarchy. The part of the structural member is setting follows natural way. The wind attack saw that building structure collapse step by step depend on its function in the structure as a whole. The lesson from Bugis in construction method is the part of the structure system best to design in the proper strength hierarchy. The strength, structure hierarchy is the maximum strength part of structure equal to the minimum strength of the structure which supports them