The Lateral Torsional Buckling of I Beams with Cross Beams

High flexural-rigid cross beams at the joints of a main beam can function as restraining members to prevent rotation during lateral torsional buckling (LTB). With less flexural-rigid members, joint rotation results in a decrease of the main beam’s LTB critical moment. This paper elucidates the cross beam’s minimum flexural rigidity to prevent the main beam’s joint rotation during torsional buckling. It is assumed that material behaves elastically, the beam’s web doesn’t undergo distortions, and shear forces effects are neglected. The cross-beam’s flexural rigidity is represented by a spiral spring. Under buckling, this spring produces a torque moment, proportional to the joint rotation. The torque will disturb the main beam’s LTB equation system. By adjusting the spring constant, the joint rotation is minimized, thus reducing the torque’s disturbing effect within the equation. By neglecting this effect, the LTB equations at all fields of main beam are identical to the general buckling equations for constant moments. For n cross beams, 4 (n+1) integration constants are resulted. By applying the boundary conditions at beam ends and utilizing the geometry and natural boundary conditions at the joints, 4 (n+1) homogeneous equations for the integration constant are obtained. By conducting the trial and error method, the critical moment resulting in a zero determinant for the homogeneous equation coefficient matrix is acquired. Then, the LTB first-mode deformation shape can be drawn. The analysis shows that to achieve the critical moment, a main beam having a cross beam located at mid span needs the most optimum (smallest) flexural rigidity of cross beam than when it is in other locations (L/2). Observing the first-mode shape, for a certain spring constant value, the rotation at the joint will approach zero

PERAN REGEL BAJA DINDTNG PENYEKAT PADA PENINGKATAN KAPASITAS KOLOM IWF

Penyekat ruangan atau dinding luar bangunan berstruktur baja sering mempergunakan regel atau balok baja kecil untuk dudukan lernbaran multiplex, metal atau harboard. Kalau regel baja terbubung secara kaku ke kolom dengan las, maka regel akan dapat berfungsi sebagai pengekang lenrur pada lenturan yang terjadi di kolom. Setiap pengekangan yang terjadi pada kolom akan berpengaruh pada besaran kapasitas kolom dalam menaban gaya dalam yang bekerja. Pengaruh ini pada umumnya oleb perencana struktur tidak pemah diperhitungkan, karena belum ada kajian secara khusus yang membahas masalah seberapa besar peran regel pada peningkatan kapasitas kolom. Dalam mengantisipasi gaya dalam terfaktoryang bekerja, perencanaan kolom yang menggunakan formulasi interaksi akan dipengaruhi oleb gaya normal nominal, momen nominal sumbu kuat dan momeo nominal sumbu lemah dari profil terpilih. Perao dari regel yang memberikan kekangan lentur pada kolom akan berpengaruh pada besaran gaya normal nominal dan Momen nominal sumbu kuat. Untuk profit kompak besaran gaya normal nominal dan momen nominal akan dipengaruhi panjang dan kondisi pengekangan kolom. Paper ini akan mengkaji seberapa jauh kontribusi kekakuan lenlur regel pada peningkatan gaya normal nominal dan momen nominal kolom. Penelitian tekuk lateral dan tekuk torsi dibatasi pada analisis kondisi elastis. Hal ini masih relevan karena formulasi tekuk Euler unruk tekuk lateral dan momen kritis untuk tekuk torsi yang dipergunakan dalam S J baja juga merupakan basil pcnjabaran analisis kondisi elastis. Analisis akan dilakukan dcngan pendekatan bahwa lentur regel bekerja pada titik berat dari profil kolom LWF. Besaran Tekuk lateral dan tekuk torsi sangat sensitip terhadap pengekangan. Kekangan regel dapat meningkatkan momen kritis dan gaya normal kritis batang cukup signifikan. Analisis akan dilakukan dengan pendekatan analitis dan numerik

Effects of Steel and Polypropylene Fiber Addition on Interface Bond Strength between Normal Concrete Substrate andSelf-Compacting Concrete Topping

Based on facts that the composite action in semi-precast and strengthened structural system depends on the bond strength of the interface between concrete faces of different ages, this preliminary research is aimed to investigate effects of mixed polypropylene (PPF) and steel fiber (SF) addition on the hardened properties of Self-Compacting Concrete (SCC) and its bond strength when used as topping layer on normal concrete substrate. Effects of hybrid fiber addition on the hardened properties of SCC were investigated based on the compressive, splitting tensile and flexural strength of concrete specimens which is tested in 28 days of age. In the next step, the tensile and shear strength of the interface were evaluated using indirect splitting tensile and bi-surface shear test method. In this research, fiber addition were prepared using 1 kg/m PPF and various SF addition ranging from 15 kg/m3, 20 kg/m3, 25 kg/m3 and 30 kg/m3. Test results indicate that hybrid fiber addition does not affect the compressive strength significantly but it leads ositive improvement to the splitting tensile and flexural strength of hardened SCC and also improve the bond strength between SCC and normal concrete. Hybrid fiber addition of 1 kg/m3 PPF which is combined with 20 kg/m3 SF can be suggested as optimum composition for Hybrid Fiber Reinforced Self-Compacting Concrete (HyFRSCC) that will be used as topping or overlay material based on its hardened properties and interface strength

The Influence of Bearing Stiffeners to Double - Symmetrical I - Section’s Torsion Stiffness, an Analytical Approach

Bearing Stiffeners are preventing web-local-buckling and reinforcing this section for point-loads and shear-forces. This paper discusses bearing stiffeners’ contribution in enhancing double-symmetric I-sections’ torsion capacity. Based on the Saint Venant’s formula torsion stresses are carried solemnly by the section, neglecting the stiffeners’ contribution. However, these stiffeners exhibit significant rotational deformation with the I-section in warping, indicating development of internal forces, restraining the warping. Therefore, the negligence of stiffeners’ contribution in Saint Venant’s torsion formula has to be revised. Torsions within the stiffeners are the Saint Venant’s and torsion-shear-stresses induced by bending. Assuming out-of-plane stresses neglected, normal and bending-shear torsion stresses are zero, leaving only the Saint Venant’s. From equilibrium at the stiffener –to-flange’s-joint, the stiffeners’ natural boundary conditions equation can be obtained. Their presence leads to a rotational-torsion function differentiation along the beam, between stiffeners. But since all points have identical internal torsion forces, the disturbed differential torsion warping equations are identical. Using the geometrical and natural boundary conditions equation the mathematical-rotational-torsion-solution for each field along the beam is obtained. It can be concluded that the member’s torsion stiffness increases approaching to linear while the increment will approach a hyperbola as a function of stiffeners’ number and thickness, respectively

Analysis of castellated steel beam with oval openings

A castellated steel beam is per definition a wide flange (WF) or I shaped steel profile with openings, to reduce self-weight and improve the effectiveness in terms of material use. Recently, extensive study on these castellated steel beams has been conducted, involving different shapes in web openings. The main goal of these research works was to evaluate and analyze its optimum opening sizes and shapes configuration. More in-depth research work to the behavior and the influence of holes to WF beams need to be conducted. In this paper, an oval shaped web opening is chosen as alternate. The study involves a modification in the variation of oval web openings both in the horizontally and vertically direction. An experimental and numerical study based on the finite element method conducted with the Abaqus/CAE 6.12 software is used to analyze the buckling behavior of the web. The obtained results from the experimental test specimens are in good agreement with the obtained results from the finite element analysis. Furthermore, the numerical model can be expanded to be used as analyzing tool in evaluating and studying the effect and influencing factors of a variation in opening’s parameters

THE STUDY OF CONCRETE WITH INDUSTRIAL STEEL-SLAG AGGREGATES BASED ON THE SUBSTITUTION METHOD

Slag is a steel-industry-waste categorized as potential environmentally harmful, containing heavy metals such as Arsenic (As), Lead (Pb), Chromium (Cr), Cuprum (Cu) and Zinc (Zn). A major Steel Plant in Semarang, Indonesia produces steel - slag that is suspected of polluting soil and groundwater. In this study attempts have been made to utilize this slag-waste as substitute for the aggregates used in concrete. Since in hardened concrete the slag will be concealed totally by the cement paste, it was hoped that the environmental impact can be controlled. The investigation was based on the substitution method whereas the coarse as well as the fine aggregates are replaced with slag. The research covers a range of concrete’ strengths and the percentage of slag substitute were set as variable. The study demonstrated that the compression-strength-to-conventional-concrete ratio increases, as the coarse slag content ascends. However, the addition of fine slag will decrease the compression strength significantly. From the results it was also proven that with a 100% of slag substitution the heavy-metal leaching concentration rate is below the assigned border mandated by the Department of Industry regulations and supports the International Atomic Energy Agency margins

Revitalization of Cracked Flexural Members using Retrofitting and Synthetic Wrapping

The modification of the Indonesia earthquake code SNI 2002 to SNI 2012 resulted in a significantly higher performance demand. The basics of these amendments lay in the re-zoning of earthquake maps, and the consideration of the earthquake influence to gravity loads. Members designed based on the SNI 2002 most likely will result in failure under future earthquakes. A reinforcement method based on the ACI 440 provision was conducted on cracked flexural members. The tensile reinforcement of these members has yielded and was neglected in the design. The tensile strains and stresses were further carried by the synthetic wraps applied to the tensile concrete fibers. The shear capacity of the member was enhanced by confinement of the member using the same synthetic wrap. Prior to wrap application, the members were straightened and retrofitted with an epoxy resin injection. The member was tested using a one-point-loading system to simulate a maximum bending moment in combination with maximum shear forces. The load-displacement responses and the ultimate load carrying capacity under monotonic incremental loading were recorded. It was found that this method will provide a solution for revitalization of cracked members in bending, and offer a solution to the design code alterations. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of SCESCM 2016

MODELLING THE TENSILE BEHAVIOR OF PLAIN CONCRETE UNDER FLEXURAL LOADING

The tensile behavior of plain concrete is customary assumed to be linear, and the stiffness modulus is approached by the value of the initial tangent stiffness modulus in compression. However, even two decades ago the contrary was proven by the experimental results on plain concrete in direct tension. The stress-strain behavior of concrete in tension was demonstrated to be highly non-linear, even at very low stress levels. One of the major difficulties in obtaining an accurate tensile stiffness response is to achieve a uniform tensile stress in the section, without creating stress concentrations at any point along the section. These stress disparities will lead to micro crack initiation and falsely recorded responses. A non-linear Finite Element Model (FEM) based on the anisotropic material approach, was developed to produce the load-displacement response of a concrete beam loaded with a two point loading system. The load-displacement curves and stress-strain curves were validated to laboratory tested specimens having identical material properties. It was shown that the stiffness behavior of plain concrete in flexure is non-linear, and follows a quadratic function. The research work also covered the evaluation of two failure criteria

ANALISA RISIKO PADA PROYEK JALAN BETON DENGAN METODE SITE MIX (STUDI KASUS : PENINGKATAN JALAN BETON KABUPATEN GROBOGAN TAHUN ANGGARAN 200

Beton sebagai lapis perkerasan jalan kaku dapat diproduksi di pabrik beton (readymix) atau diproduksi di lokasi pekerjaan (site mix ). Pada pekerjaan beton site mix terdapat risiko cukup besar yang dapat mempengaruhi pencapaian kualitas beton. Proyek peningkatan jalan beton di Kabupaten Grobogan Tahun Anggaran 2008 sebagian besar menggunakan beton site mix , terjadi kerusakan beton seperti permukaan jalan yang aus dan berlubang. Kerusakan yang terjadi dapat disebabkan adanya faktor risiko pada bahan penyusun beton, pencampuran bahan, pelaksanaan pengecoran dan pada perawatan beton serta dapat dipengaruhi oleh pengendalian kualitas selama pelaksanaan. Tujuan penelitian ini adalah mengkaji hubungan antara sumber risiko (x1), pengendalian (x2) dan kualitas (y) pada beton site mix dan menentukan faktor risiko yang muncul sebagai sumber risiko pada beton site mix . Faktor risiko kemudian dikelompokkan sesuai kategori risiko, yang dibagi dalam empat kategori yaitu risiko high, significant, moderate dan low. Metode penelitian ini dengan cara distribusi kuesioner kepada Dinas Bina Marga Kabupaten Grobogan. Sebagai data pendukung digunakan data hasil uji beton di lokasi yaitu pengujian hammer dan pengujian core drill. Kombinasi pengujian hammer dan core drill dibuat suatu kurva tertentu pada grafik rebound - strength (MPa) yang digunakan sebagai pendukung pencapaian kualitas beton site mix . Berdasarkan analisa hubungan antara sumber risiko (x1) dan pengendalian (x2) terhadap kualitas (y), diperoleh hasil bahwa kualitas beton tidak banyak dipengaruhi oleh adanya risiko tetapi lebih dominan dipengaruhi oleh pengendalian selama pekerjaan. Hasil pemetaan risiko menunjukkan bahwa faktor risiko kadar lumpur pada pasir, pelaksanaan campuran harus sesuai job mix, ketelitian alat penakar, perlindungan selama pengecoran, pemadatan dan perawatan beton termasuk kategori risiko high (H). Faktor risiko sumber dan kualitas air yang digunakan, Faktor Air Semen (FAS), ketelitian proporsi dan perlindungan arus lalu lintas termasuk kategori risiko Significant (S). Faktor risiko berat kemasan semen (kg/zak), ketelitian penakar dan volume air, properties agregat, pelaksanaan pencampuran dan metode pengecoran termasuk kategori risiko Moderate (M). Sedangkan pada kategori Low (L) tidak ditemukan faktor risiko pada kategori tersebut. Semua faktor risiko tersebut perlu pengendalian rutin untuk menjaga kualitas beton sesuai spesifikasi. Dari pengujian hammer sebanyak 862 titik didapatkan kuat tekan rata-rata sebesar 305,72 kg/cm2. Dari pengujian core drill sebanyak 82 titik didapatkan kuat tekan rata-rata sebesar 77,04 kg/cm2. Evaluasi mutu beton dengan kurva pada grafik rebound - strength, didapatkan hasil kuat tekan beton sebesar 182,40 kg/cm2 (≈15,14 MPa). Mutu beton yang lebih rendah dari spesifikasi (300 kg/cm2) menyebabkan kondisi jalan beton mengalami kerusakan. Kualitas beton site mix tidak dipengaruhi sumber risiko secara langsung, tetapi lebih dominan dipengaruhi oleh pengendalian. Karena faktor-faktor risiko pada bahan penyusun beton dan pelaksanaannya dianggap bukan sebagai faktor yang dapat mempengaruhi kualitas beton site mix

Experimental Study on Shear Capacity of RC Beams Strengthened With Carbon Fiber Reinforced Polymer Mandated by ACIi 440

Shear reinforcement for retrofitting a reinforced concrete (RC) beam using unidirectional Carbon Fiber Reinforced Polymer (CFRP) woven can only be applied on the beam web below the concrete floor slab. Thus, it cannot fully confine like the way stirrups do, in which it will affect the shear capacity. The CFRP can only be ‘n’or ‘u’ shaped, taking into consideration the direction of shear force. Herein, the experimental study of the shear capacity of shear capacity the beam strengthened by FRP is carried out.shear capacity. The beams are RC beams of width 150 mm, height 300 mm, span of 1000 mm, f'c = 26 MPa having 2 bar of 19 mm diameter (fy = 403.65 MPa) and stirrups 6 mm diameter of 250 mm spacing (fy=375 MPa). The shear capacity measured is then compared with the shear capacity calculated using ACI 440. The result shows that the shear capacity measured from experiment is greater than the shear capacity calculated by ACI 440. Also, the shear capacity of RC beam with CFRP reinforcement n shape is greater than u shape